WO2015062669A1

WO2015062669A1 - Signal processing

Info

Publication number: WO2015062669A1
Application number: PCT/EP2013/072868
Authority: WO
Inventors: Gunter Wolff; Hans Dieterich
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2013-11-01
Filing date: 2013-11-01
Publication date: 2015-05-07

Abstract

There is provided an apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to at least: spread and scramble an input signal having a first bandwidth to form a spread signal having a second bandwidth, the second bandwidth being larger than the first bandwidth; wherein the spread signal comprises a first part and a redundant part.

Description

Description Title Signal processing

This disclosure relates to spread signals.

Code division multiple access (CDMA) is a technology that allows different user data streams to be transmitted simultaneously in the same frequency range. The separation between the different data streams is achieved by spreading codes, with each data stream being associated with a respective spreading code. CDMA is also utilized in the field of mobile communication. In particular, the Universal Mobile Telephony System (UMTS) utilises wideband-CDMA (WCDMA). There is a limited amount of frequency bandwidth available in a communication system as there are a number of communication protocols competing for use of the frequency bandwidth. In certain circumstances, the frequency bandwidth may be re-farmed (i.e. used by other communication protocols/systems operating within the same frequency band(s)). Aggressive re-farming of frequency resources can thus lead to a reduced carrier bandwidth for a particular communication protocol. This increases interference and reduces throughput. For WCDMA, even bandwidths below the chip rate of 3.84 MS/s (Mega Symbols per second) are envisaged.

Excessive bandwidth reduction may destroy the orthogonality between the spreading codes and may considerably increase cross talk between different data streams.

According to a first aspect, there is provided an apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to at least: spread and scramble an input signal having a first bandwidth to form a spread signal having a second bandwidth, the second bandwidth being larger than the first bandwidth; wherein the spread signal comprises a first part and a redundant part. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to cause the transmission of at least the first part and no more than part of the redundant part. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to spread the input signal by applying a spreading code to the input signal, the spreading code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to spread the input signal by applying a spreading code to the input signal to form a first processed signal, and to subsequently manipulate the first processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to scramble the input signal by applying a scrambling code to the input signal, the scrambling code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to scramble the input signal by applying a scrambling code to the input signal to form a second processed signal, and to subsequently manipulate the second processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

The predetermined feature may be a zero. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to repeat the predetermined signal periodically in the spread signal.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to form the redundant part of the spread signal such that it replicates at least part of the relevant part. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to filter the spread signal to form a filtered signal and to output the filtered signal for transmission.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to filter the spread signal using a filter bandwidth that is smaller than the second bandwidth. The at least one memory and the computer program code may be configure to, with the at least one processor, cause the apparatus to filter the spread signal using a filter bandwidth that is smaller than the bandwidth of the first part.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to form the first part of the spread signal such that the first part has a smaller bandwidth than the second bandwidth.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to spread the input signal prior to scrambling the input signal. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to scramble the signal by applying a scrambling code, the scrambling code being such that only every second bit has a nonzero value The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to scramble the signal by applying a scrambling code, the scrambling code being such only one in four bits has a non-zero value.

The non-zero values may originate from a Gold code that identifies the apparatus and the at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to form the scrambling code by sampling the Gold code.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to form the scrambling code using multiple repetitions of a scrambling code defined by a communication protocol,

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to spread the signal by applying a spreading code, the spreading code being such that only every second bit has a non-zero value

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to spread the signal by applying a spreading code, the spreading code being such only one in four bits has a non-zero value.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to form the spreading code using multiple repetitions of a spreading code defined by a communication protocol. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to use only a subset of spreading codes from a plurality of spreading codes defined by a communication protocol for spreading the input signal. There is also provided a method comprising: spreading and scrambling an input signal having a first bandwidth to form a spread signal having a second bandwidth, the second bandwidth being larger than the first bandwidth; wherein the spread signal comprises a first part and a redundant part. According to a second aspect there is provided an apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to at least: de-scramble and de-spread an input signal to form a de-spread signal; wherein the de-spread signal comprises a first part and a redundant part. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to insert the redundant part during at least one of the de-scramble, and the de-spread operations. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to de-spread the input signal by applying a de-spreading code to the input signal, the de-spreading code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to de-spread the input signal by applying a de-spreading code to the input signal to form a first processed signal, and to subsequently manipulate the first processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de- spread signal.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to de-scramble the input signal by applying a de-scrambling code to the input signal, the de-scrambling code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to de-scramble the input signal by applying a de-scrambling code to the input signal to form a second processed signal, and to subsequently manipulate the second processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

The predetermined feature may be a zero.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to repeat the predetermined signal periodically in the de-spread signal. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to form the redundant part of the de-spread signal such that it replicates at least part of the relevant part. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to filter the input signal to form a filtered signal and to output the filtered signal for de-spreading and de-scrambling.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to de-scramble the input signal prior to de- spreading the input signal.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to de-scramble the signal by applying a de- scrambling code, the de-scrambling code being such that only every second bit has a nonzero value

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to de-scramble the signal by applying a de- scrambling code, the de-scrambling code being such only one in four bits has a non-zero value.

The non-zero values may originate from a Gold code that identifies the apparatus and the at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to form the de-scrambling code by sampling the

Gold code.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to form the de-scrambling code using multiple repetitions of a de-scrambling code defined by a communication protocol,

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to de-spread the signal by applying a de- spreading code, the de-spreading code being such that only every second bit has a non- zero value The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to de-spread the signal by applying a de- spreading code, the de-spreading code being such only one in four bits has a non-zero value.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to form the de-spreading code using multiple repetitions of a de-spreading code defined by a communication protocol. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to use only a subset of de-spreading codes from a plurality of de-spreading codes defined by a communication protocol.

There is also provided a method comprising: de-scrambling and de-spreading an input signal to form a de-spread signal, wherein the de-spread signal comprises a first part and a redundant part.

The method may comprise inserting the redundant part during at least one of the de- scramble, and the de-spread operations.

The method may comprise de-spreading the input signal by applying a de-spreading code to the input signal, the de-spreading code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de- spread signal.

The method may comprise de-spreading the input signal by applying a de-spreading code to the input signal to form a first processed signal, and subsequently manipulating the first processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

The method may comprise de-scrambling the input signal by applying a de-scrambling code to the input signal, the de-scrambling code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal. The method may comprise de-scrambling the input signal by applying a de-scrambling code to the input signal to form a second processed signal, and subsequently manipulating the second processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de- spread signal.

The predetermined feature may be a zero.

The method may comprise repeating the predetermined signal periodically in the de- spread signal.

The method may comprise forming the redundant part of the de-spread signal such that it replicates at least part of the relevant part. The method may comprise filtering the input signal to form a filtered signal and to output the filtered signal for de-spreading and de-scrambling.

The method may comprise de-scrambling the input signal prior to de-spreading the input signal.

The method may comprise de-scrambling the signal by applying a de-scrambling code, the de-scrambling code being such that only every second bit has a non-zero value

The method may comprise de-scrambling the signal by applying a de-scrambling code, the de-scrambling code being such only one in four bits has a non-zero value.

The non-zero values may originate from a Gold code that identifies an apparatus executing the method and the method may comprise forming the de-scrambling code by sampling the Gold code.

The method may comprise forming the de-scrambling code using multiple repetitions of a de-scrambling code defined by a communication protocol,

The method may comprise de-spreading the signal by applying a de-spreading code, the de-spreading code being such that only every second bit has a non-zero value The method may comprise de-spreading the signal by applying a de-spreading code, the de-spreading code being such only one in four bits has a non-zero value.

The method may comprise forming the de-spreading code using multiple repetitions of a de-spreading code defined by a communication protocol.

The method may comprise de-spreading using only a subset of de-spreading codes from a plurality of de-spreading codes defined by a communication protocol. According to a third aspect, there is provided a system comprising: the apparatus of claim 1 configured to cause the transmission of the relevant part to the spread signal; and the apparatus of claim 1 1 configured to receive said transmission from the apparatus of claim 1 as an input signal for the de-scramble and de-spread. There is also provided a computer program comprising code means adapted to cause performing of the method of claim 19 when the program is run on data processing apparatus.

There is also provided a computer program comprising code means adapted to cause performing of the method of claim 34 when the program is run on data processing apparatus.

According to another aspect, there is provided an apparatus comprising means for spreading and scrambling an input signal having a first bandwidth to form a spread signal having a second bandwidth, the second bandwidth being larger than the first bandwidth; wherein the spread signal comprises a first part and a redundant part.

The apparatus may comprise means for causing the apparatus to cause the transmission of at least the first part and no more than part of the redundant part.

The apparatus may comprise means for spreading the input signal by applying a spreading code to the input signal, the spreading code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal. The apparatus may comprise means for spreading the input signal by applying a spreading code to the input signal to form a first processed signal, and for subsequently manipulating the first processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

The apparatus may comprise means for scrambling the input signal by applying a scrambling code to the input signal, the scrambling code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

The apparatus may comprise means for scrambling the input signal by applying a scrambling code to the input signal to form a second processed signal, and for subsequently manipulating the second processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

The predetermined feature may be a zero. The apparatus may comprise means for repeating the predetermined signal periodically in the spread signal.

The apparatus may comprise means for forming the redundant part of the spread signal such that it replicates at least part of the relevant part.

The apparatus may comprise means for filtering the spread signal to form a filtered signal and to output the filtered signal for transmission.

The apparatus may comprise means for filtering the spread signal using a filter bandwidth that is smaller than the second bandwidth. The apparatus may comprise means for filtering the spread signal using a filter bandwidth that is smaller than the bandwidth of the first part.

The apparatus may comprise means for forming the first part of the spread signal such that the first part has a smaller bandwidth than the second bandwidth. The apparatus may comprise means for forming the first part of the spread signal such that the first part has a smaller bandwidth than the second bandwidth.

The apparatus may comprise means for spreading the input signal prior to scrambling the input signal.

The apparatus may comprise means for scrambling the signal by applying a scrambling code, the scrambling code being such that only every second bit has a non-zero value The apparatus may comprise means for scrambling the signal by applying a scrambling code, the scrambling code being such only one in four bits has a non-zero value.

The non-zero values may originate from a Gold code that identifies the apparatus and the at least one memory and the apparatus may comprise means for forming the scrambling code by sampling the Gold code.

The apparatus may comprise means for forming the scrambling code using multiple repetitions of a scrambling code defined by a communication protocol, The apparatus may comprise means for spreading the signal by applying a spreading code, the spreading code being such that only every second bit has a non-zero value

The apparatus may comprise means for spreading the signal by applying a de-spreading code, the spreading code being such only one in four bits has a non-zero value.

The apparatus may comprise means for forming the spreading code using multiple repetitions of a spreading code defined by a communication protocol.

The apparatus may comprise means for using only a subset of spreading codes from a plurality of spreading codes defined by a communication protocol.

There is also provided a method comprising: spreading and scrambling an input signal having a first bandwidth to form a spread signal having a second bandwidth, the second bandwidth being larger than the first bandwidth; wherein the spread signal comprises a first part and a redundant part. The method may further comprise causing the transmission of at least the first part and no more than part of the redundant part.

The method may further comprise spreading the input signal by applying a spreading code to the input signal, the spreading code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

The method may further comprise spreading the input signal by applying a spreading code to the input signal to form a first processed signal, and subsequently manipulating the first processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

The method may further comprise scrambling the input signal by applying a scrambling code to the input signal, the scrambling code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

The method may further comprise scrambling the input signal by applying a scrambling code to the input signal to form a second processed signal, and subsequently manipulating the second processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal. The predetermined feature may be a zero.

The method may further comprise repeating the predetermined signal periodically in the spread signal. The method may further comprise forming the redundant part of the spread signal such that it replicates at least part of the relevant part.

The method may further comprise filtering the spread signal to form a filtered signal and to output the filtered signal for transmission. The method may further comprise filtering the spread signal using a filter bandwidth that is smaller than the second bandwidth. The apparatus may comprise means for filtering the spread signal using a filter bandwidth that is smaller than the bandwidth of the first part. The method may further comprise forming the first part of the spread signal such that the first part has a smaller bandwidth than the second bandwidth.

The method may further comprise forming the first part of the spread signal such that the first part has a smaller bandwidth than the second bandwidth.

The method may further comprise spreading the input signal prior to scrambling the input signal.

The method may further comprise scrambling the signal by applying a scrambling code, the scrambling code being such that only every second bit has a non-zero value

The method may further comprise scrambling the signal by applying a scrambling code, the scrambling code being such only one in four bits has a non-zero value. The non-zero values may originate from a Gold code that identifies an apparatus executing the method and the method may further comprise forming the scrambling code by sampling the Gold code.

The method may further comprise forming the scrambling code using multiple repetitions of a scrambling code defined by a communication protocol.

The method may further comprise de-spreading the signal by applying a spreading code, the spreading code being such that only every second bit has a non-zero value The method may further comprise de-spreading the signal by applying a spreading code, the spreading code being such only one in four bits has a non-zero value.

The method may further comprise forming the spreading code using multiple repetitions of a spreading code defined by a communication protocol. The method may further comprise using only a subset of spreading codes from a plurality of spreading codes defined by a communication protocol for spreading the input signal.

According to another aspect there is provided an apparatus comprising: means for de- scrambling and de-spreading an input signal to form a de-spread signal; wherein the de- spread signal comprises a first part and a redundant part.

The apparatus may comprise means for inserting the redundant part during at least one of the de-scramble, and the de-spread operations.

The apparatus may comprise means for de-spreading the input signal by applying a de- spreading code to the input signal, the de-spreading code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

The apparatus may comprise means for de-spreading the input signal by applying a de- spreading code to the input signal to form a first processed signal, and for subsequently manipulating the first processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de- spread signal.

The apparatus may comprise means for de-scrambling the input signal by applying a de- scrambling code to the input signal, the de-scrambling code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

The apparatus may comprise means for de-scrambling the input signal by applying a de- scrambling code to the input signal to form a second processed signal, and for subsequently manipulating the second processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

The predetermined feature may be a zero. The apparatus may comprise means for repeating the predetermined signal periodically in the de-spread signal. The apparatus may comprise means for forming the redundant part of the de-spread signal such that it replicates at least part of the relevant part. The apparatus may comprise means for filtering the input signal to form a filtered signal and to output the filtered signal for de-spreading and de-scrambling.

The apparatus may comprise means for de-scrambling the input signal prior to de- spreading the input signal.

The apparatus may comprise means for de-scrambling the signal by applying a de- scrambling code, the de-scrambling code being such that only every second bit has a nonzero value The apparatus may comprise means for de-scrambling the signal by applying a de- scrambling code, the de-scrambling code being such only one in four bits has a non-zero value.

The non-zero values may originate from a Gold code that identifies the apparatus and the at least one memory and the apparatus may comprise means for forming the de- scrambling code by sampling the Gold code.

The apparatus may comprise means for forming the de-scrambling code using multiple repetitions of a de-scrambling code defined by a communication protocol,

The apparatus may comprise means for de-spreading the signal by applying a de- spreading code, the de-spreading code being such that only every second bit has a nonzero value The apparatus may comprise means for de-spreading the signal by applying a de- spreading code, the de-spreading code being such only one in four bits has a non-zero value.

The apparatus may comprise means for forming the de-spreading code using multiple repetitions of a de-spreading code defined by a communication protocol. The apparatus may comprise means for using only a subset of de-spreading codes from a plurality of de-spreading codes defined by a communication protocol.

Embodiments will now be described in further detail, by way of example only, with reference to the following examples and accompanying drawings, in which:

Figure 1 shows a schematic diagram of a system where certain embodiments can be implemented;

Figure 2A shows an example of a user device;

Figure 2B shows an example of a control apparatus;

Figure 3 shows a system architecture;

Figure 4 is a code generation tree;

Figure 5 is a graph illustrating frequency re-farming;

Figure 6 depicts a process;

Figure 7 depicts a signal;

Figure 8 depicts an example system;

Figure 9 depicts an example transmitter;

Figure 10 depicts an example receiver;

Figures 1 1 to 14 depict example transmitters;

Figures 15 to 18 depict example receivers;

Figure 19 depicts an example signal; and

Figures 20 to 22 illustrate time-varying gain.

The following relates to an apparatus configured to spread and scramble an input signal to form a spread signal for transmission. The spread signal has a first part and a redundant part. Preferably the redundant part is unnecessary for reconstructing the original input signal.

By constructing a signal having a redundant part, this means that it is less important if the frequency bandwidth of the transmit filter is configured to be smaller than the spreading code (for example, in the case where there is frequency re-farming as described above). In other words, the transmit filter may have a frequency bandwidth that is much less than the frequency bandwidth of the spread signal, and yet the original data stream can be reconstructed on the receive side with minimal manipulation of the received signal. The manipulation of the signal such that the de-scrambled and/or de-spread signal in the receiver comprises a first part and a redundant part may be executed using software to avoid physically modifying the transmitter and/or receiver.

There may be provided a receiver configured to operate in such a system to recover the input signal of the transmitter. The receiver is configured to de-scramble and to de-spread a received signal to form de-scrambled and/or a de-spread signal having a first part and a redundant part.

In the following certain exemplifying embodiments are explained with reference to a system that serves wireless or mobile communication devices as well as user devices that are communicating via fixed connections. Therefore, before explaining in detail the exemplifying embodiments, certain general principles of a communication system and access thereto, and communication devices are briefly explained with reference to Figures 1 to 2B to assist in understanding the technology underlying the described examples.

A communication system can be seen as a facility that enables communications between two or more nodes such as fixed or mobile communication devices, access points such as base stations, servers and so on. Signals can be carried on wired or wireless carriers. Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). A user can access the communication system by means of an appropriate communication device or terminal. A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. Typically a communication device is used for enabling receiving and transmission of communications such as voice, images, video and other data. A communication device of a user is often referred to as a user equipment (UE). Communication devices or terminals can be provided wireless access via base stations or similar wireless transmitter and/or receiver nodes providing radio service areas or cells. In Figure 1 wireless connectivity is shown being provided by base stations 1 1 , 13, 15 and 17. The wireless communication devices 10, 20 and 21 may comprise any suitable device capable of wireless communication of data. A fixedly connected user terminal 12 is also shown.

The user can be provided with various services via a communication system and terminal devices. Non-limiting examples of the services include two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. In the herein described scenario current the users are provided with the possibility to experience media content such as music, videos, multimedia and so on based on playlists managed by a controller 16 in a data network system 14. A more particular example of such services is streaming services. In the herein described examples the streaming service enables social interaction between the users. The controller can be provided e.g. by an application server managed by a service provider.

A possible mobile communication device for transmitting and retransmitting information blocks towards the stations of the system will now be described in more detail in reference to Figure 2 showing a schematic, partially sectioned view of a communication device 200. Such a communication device is often referred to as user equipment (UE) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples include a mobile station (MS) such as a mobile phone or what is known as a 'smart phone', a portable computer provided with a wireless interface card or other wireless interface facility, personal data assistant (PDA) provided with wireless communication capabilities, or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services include two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. User may also be provided broadcast or multicast data. Non-limiting examples of the content include downloads, television and radio programs, videos, advertisements, various alerts and other information. The mobile device may receive signals over an air interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

A mobile device is also typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204.

The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

Figure 2B shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system. In some embodiments base stations comprise a separate control apparatus. In other embodiments the control apparatus can be another network element. The control apparatus 220 can be arranged to provide control on communications in the service area of the system. The control apparatus 220 can be configured to provide control functions in association with retransmission and muting by means of the data processing facility in accordance with certain embodiments described below. For this purpose the control apparatus comprises at least one memory 221 , at least one data processing unit 222, 223 and an input/output interface 224. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The control apparatus can be configured to execute an appropriate software code to provide the control functions. It shall be appreciated that similar component can be provided in a control apparatus provided elsewhere in the system for controlling reception of sufficient information for decoding of received information blocks.

Communication devices can access the communication system based on various access techniques, such as code division multiple access (CDMA), or wideband CDMA (WCDMA). Other examples include time division multiple access (TDMA), frequency division multiple access (FDMA) and various schemes thereof such as the interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA) and so on. A wireless device can be provided with a Multiple Input / Multiple Output (MIMO) antenna system. MIMO arrangements as such are known. MIMO systems use multiple antennas at the transmitter and receiver along with advanced digital signal processing to improve link quality and capacity. Although not shown in Figures 1 and 2A and 2B, multiple antennas can be provided at the relevant nodes, for example at base stations and mobile stations, and the transceiver apparatus 206 of Figure 2A can provide a plurality of antenna ports. More data can be received and/or sent where there are more antennae elements.

The following describes particular examples using the system set up and terminology employed by WCDMA. However, it is understood to the skilled person that the principles outlined in relation to these examples may also be applied to other systems. In particular, the following principles may be applied to other CDMA systems.

Figure 3 illustrates the signal flow for spreading, scrambling and transmitting an input signal in a transmitter in a WCDMA system and for receiving, de-scrambling and de- spreading a signal in a receiver in a WCDMA system. As shown in Figure 3, multiple incoming data streams A1 ... Am are input to a spreader 301 . The spreader outputs a signal B to a scrambler 302. The scrambler 302 outputs a signal C to a transmission filter 303. The transmission filter 303 outputs a signal D for transmission to a receiver. The receiver comprises a receive filter 304, which receives signal D (ignoring any modifications to the signal D introduced during transmission) and outputs signal E to a de- scrambler 305 in the receiver. The de-scrambler 305 receives the signal E and outputs a signal F to a de-spreader 306 in the receiver. The de-spreader 306 receives the signal F and outputs multiple data streams G1 ... Gm for further processing in the receiver.

In operation, the spreader is configured to multiply each incoming user data stream A1 ... Am by a respective spreading code. Each data stream comprises a plurality of data bits, which convey information. By multiplying a data stream by a spreading code, the data rate of the data stream increases by a spreading factor. In other words, the frequency bandwidth of the data stream increases by the spreading factor. The spreading factor is related to the length of the spreading code. For example, if an incoming data stream has a bit sequence of rate R, and each data bit in the stream is multiplied by N chips, then the resulting spread data is at a rate of NxR. In WCDMA, the spreading code is called a "channelization code" and is described more fully in 3GPP S 25.213 (spreading and modulation). As described therein, a respective channelization code is applied to each data stream by multiplying each data stream by its respective channelization code in order to spread each data stream to a respective bandwidth. Each data stream is preferably spread to the same bandwidth using different channelization codes. The channelization codes are orthogonal variable spreading factor codes. The code tree for generating these codes in WCDMA/UMTS is illustrated in Figure 4. Each channel code is labelled using two variables, "n" and "k". "n" is an integer greater than one and, at each stage of the code tree, increases by twice its previous value. For example, at the first branch, "n" is 1 and there is one limb having a code of (1 ). At the second branch, "n" is 2 (1 X2) and there are two limbs having respective codes of (1 ,1 ) and (1 ,-1 ). At the third branch, "n" is 4 (2x2) and there are four limbs having respective codes of (1 , 1 , 1 ,1 ), (1 , 1 ,-1 ,-1 ), (1 ,-1 ,1 ,-1 ) and (1 ,-1 ,-1 , 1 ). And so on. "k" is an integer spanning the range from "0" to "n-1 ". Each limb of the code tree begets two limbs on the subsequent branch. Assuming the code of a particular limb is Dm, where Dm is a vector, the codes of the limbs begot by that particular limb are Dm. (1 , 1 ) and Dm.(1 ,-1 ) respectively. The spreader 301 is further configured to sum all of the spread signals together to form a composite signal B. The composite signal B is output to the scrambler 302. In the present example, all the data streams have a common chip rate of 3.84 MS/s after spreading. The scrambler 302 is configured to multiply the signal B by a scrambling code that identifies the transmitter. Thus it can be said that scrambling codes are used to make signals from different transmitters separable from each other. In WCDMA, the scrambling code is an orthogonal code that is much longer than any of the spreading codes. There is no correlation between spreading and scrambling. Further, scrambling does not affect the transmission bandwidth. The scrambled signal is labelled as signal C in Figure 3 and is output to a transmission filter 303. As scrambling does not affect the transmission bandwidth, signal C has the same symbol rate as signal B i.e. 3.84 MS/s.

The signal C is filtered by a transmission filter 303 and subsequently transmitted as signal D. In the example of Figure 3, the transmission filter is a root raised cosine (RRC) filter having a bandwidth of 3.84 MHz and a roll-off factor of 0.22. The impact of the channel on signal D is neglected in this simplified view.

In the example of Figure 3, the receive filter 304 is an RRC filter with 3.84 MHz bandwidth and a roll-off factor of 0.22. The receive filter 304 receives transmitted signal D and filters signal D to output signal E to a de-scrambler 305. The signal E appears to be raised cosine (RC) filtered against a signal corresponding to the oversampled signal C. After decimation back to 3.84 MS/s, signal E should be the same as signal C. The de-scrambler 305 de-scrambles the decimated signal E to output a signal F. The de- scrambling code is the complex conjugate of the scrambling code. Thus signal F should correspond to signal B. The signal F is input to a de-spreader 306, which de-spreads the signal F using de-spreading codes to output the data streams G1 ... Gm. Since the de- spreading codes (and the spreading codes) are orthogonal, only the corresponding data stream for a particular de-spreading code is extracted from the composite signal F when that de-spreading code is applied. As mentioned above, there can be a limited amount of frequency bandwidth available in a communication system as there are a number of communication protocols competing for use of the frequency bandwidth (e.g. such as during re-farming). For WCDMA, usable carrier bandwidths below the chip rate of 3.84 MS/s are envisaged. This is illustrated in Figure 5.

Figure 5 is a graph having frequency in Hz along the x-axis and power spectral density (PSD) in W/Hz along the y-axis. The "usual carrier bandwidth" (i.e. the bandwidth the transmitter is supposed to transmit at in accordance with its operating communication protocol) is indicated by a signal 501. The chip rate, determined by the result of the spreading operation, is indicated by the lines 502. The lines 502 are parallel to each other and each bisect a respective extremity of the usual carrier bandwidth. The shrunken carrier bandwidth, which is determined in dependence on the amount of re-farmed of frequency resources, is indicated by the signal 503. In Figure 5, the shrunken carrier bandwidth is approximately half of the usual carrier bandwidth.

Excessive bandwidth reduction may destroy the orthogonality between the spreading codes and can considerably increase cross talk between different data streams.

One way to address the problem of excessive bandwidth reduction is to reduce the chip rate in the spreading code. This results in a smaller frequency bandwidth for transmission as the frequency bandwidth is reduced by the same factor as the chip rate. However, this solution may require new hardware.

A technique that may be implemented using legacy hardware with minor software adaptations is thus preferable. The following described examples may be implemented using legacy hardware and/or minor software changes. However, it should be noted that the principles of the following examples may be implemented using new hardware.

In the following examples described in relation to figures 6 to 18, the usable frequency bandwidth is half the frequency bandwidth of the spread signal (although it is noted that the actual usable frequency bandwidth could be any fraction of the spread signal). The below described transmitters are thus configured to form a scrambled signal for transmission having all relevant information provided in the usable frequency bandwidth and redundant information provided outside of the usable frequency bandwidth. On the receiver side, the redundant information is known (or can be determined). The receiver may therefore, on receiving a transmission comprising the relevant information, reconstruct the input signal by inserting the redundant information therein. These operations may be performed in a variety of ways, as described below. In the following, an unfiltered WCDMA signal C (see Figure 4) is synthesised at an original chip rate prescribed by the UMTS/WCDMA protocol i.e. 3.84 MS/s

This synthesized signal passes through a transmission filter having a reduced bandwidth (such as from re-farming of the carrier frequency band). Even though the bandwidth of the transmission filter is reduced significantly, the WCDMA signal is synthesized so that very little, if any, relevant information is lost by passing the signal through the transmission filter.

In the following example, described below in relation to Figures 6 to 10, the transmission filter is a 3 dB root raised cosine filter having an RRC filter bandwidth of 1.96MHz i.e. having half the original 3 dB RRC filter bandwidth of 3.84 MHz mentioned above in relation to Figure 3. Further, the signal C is configured to have a relevant part and a redundant part by arranging certain bits in the signal to take on a particular value. In particular, as the filter bandwidth of this system is half the frequency bandwidth of the signal C, the signal C is arranged such that every other bit has a predetermined value.

The process employed by the transmitter and receiver of the present example is described in relation to Figure 6.

At 601 , the process starts. At 602, a stream of user data A_k is input to a spreader in a transmitter. The spreader is configured to duplicate the stream of user data A_k so as to create two identical streams of user data A_k. At 603, the spreader synthesises a signal B_n,k using the two identical data streams A_k utilizing the channelization codes C_Ch,2ⁿ,_k and C_Ch,2ⁿ,_k+2ⁿ-¹ (n≥1 , k = 0 ...2^n"1-1 ). This creates a signal, wherein every second sample is equal to zero. For example, n = 2 and k=1 yields:

B₂,1 = A_k-Cch,2ⁿ,k + A_k-C_ch,₂n,_k+2ⁿ-¹ =

-(1 ,-1 ,-1 , 1 ) =

A₁ -(2,0,-2,0)

At 604, all of the synthesised signals B_n,k are summed to create a spread signal B of Figure 3. The spread signal B is output to a scrambler in the transmitter. Since every second sample is equal to zero inside B_n,k and the zero positions coincide, this also holds for the superposition of different B_n,k. Hence, B =∑B_n,k appears as if it was generated at half the sample rate and aliased. This means that the information of the inner 1.92 MHz is replicated just outside this inner frequency range. This principle is shown in Figure 7.

In Figure 7, there is depicted a graph having frequency (in Hertz) along the x-axis and power spectral density (in Watts per Hz) along the y-axis. The total spread signal is indicated by the numeral 701. The total spread signal can be split up into two sections: a relevant data part (labelled as 704 and 705); and a redundant data part (labelled as 706 and 707). The relevant data part 704 is identical to the redundant data part 706. The relevant data part 705 is identical to the redundant data part 707. As the total signal comprises a replica of the relevant data parts 704, 705, the total signal may be described as being "aliased". The relevant data parts 704, 705 are centred around the centre of the reduced usable bandwidth "W" of the system. The system has reduced usable bandwidth due, for example, to frequency/carrier re-farming. The bandwidth of the filter is also centred around the centre of the reduced usable bandwidth "W" of the system. If only aliased signals are used then, regardless of the location of the frequency window, all of the relevant information is available in a frequency range centred on the centre of the usable carrier frequency bandwidth. For example, when half of a 3.84MHz bandwidth is usable, all of the relevant information is available in a 1.92 MHz wide frequency range. The other signal frequency range is simply a replica of that information. At 605, the spread, summed signal B is input to the scrambler in the transmitter and scrambled using a scrambling code. The scrambling code identifies the transmitter that will be transmitting the spread, summed and scrambled signal. At 606, the scrambler outputs a signal C. Like the signal B, the signal C appears to have every second sample equal to zero. Also, as mentioned in the background section, scrambling does not affect the frequency bandwidth occupied by the signal. Hence, the scrambled signal C also appears to be aliased and contains all its relevant information in the inner 1 .92 MHz range.

At 607, the signal C is input to a transmission filter in the transmitter. Since, in the present example, the transmission filter bandwidth is 1.92 MHz and all of the relevant information is comprised within the inner 1 .92 MHz frequency bandwidth, no information is lost by filtering the signal C. Passing the signal C through the transmission filter results in a signal D being output.

At 607, the signal D is transmitted by the transmitter through a wireless communication medium to at least one receiver (hereinafter termed "the receiver"). At 608, the receiver receives the signal D through the wireless communication medium.

At 609, the received signal D is passed through a receive filter in the receiver. Since, in the present example, the receive filter bandwidth is 1.92MHz, which corresponds to the bandwidth of the relevant information in the signal transmitted by the transmitter, no relevant information is lost by filtering the signal D. Passing the received signal D through the receive filter results in a signal E being output.

At 610, the signal E is input to a de-scrambler in the receiver and de-scrambled to produce a signal F. The signal F corresponds to the original signal B. As it is known that every second bit of signal B is zero, additional zeroes may be inserted into the signal when de-scrambling the signal E to form the signal F. In particular, every second bit of signal F shall be forced to be zero in order to reconstruct the alias signal components

At 61 1 , the signal F is input to a de-spreader in the receiver for de-spreading. In other words, the signal F is input to a de-spreader to reproduce the original data-streams A1 ... Am. The different data streams on the receiver's side are labeled as G1 ... Gm, and are equivalent with the streams A1 ... Am. For de-spreading it is sufficient to use only the subset of the spreading codes C_ch,2ⁿ,k (n≥1 , k = 0 ...2^n"1-1 ). As, in this embodiment, the usual carrier bandwidth is reduced by a factor of 1/2, the subset of de-spreading codes contains all the spreading codes that do not block each other (see below) resulting from a bandwidth reduction of 1/2.

At 612 the process ends.

An example transmitter-receiver architecture for implementing the steps of Figure 6 is illustrated in Figure 8.

In Figure 8, there is provided a transmitter comprising a duplicator 801 , a spreader 802, a scrambler 803 and a transmission filter 804. The duplicator 801 is configured to receive multiple data streams A1 , A2... Am and to output two copies of this incoming data stream i.e. to output A1 , A1 , A2, A2... Am, Am to the spreader 802. The spreader 802 is configured to receive the two copies of the data stream and to apply spreading codes to the data streams as described above in relation to step 603 of Figure 6. The spread signals are summed together to form a signal B. The signal B is output by the spreader to a scrambler 803. The scrambler 803 is configured to apply a scrambling code to the summed signal B by multiplying the summed signal B by the scrambling code. The scrambling code identifies the transmitter. The scrambler outputs a scrambled version of the spread signal B as a scrambled signal C to the transmission filter 804. The transmission filter filters the signal C and outputs a signal D for transmission over a wireless transmission medium.

The receiver comprises a receive filter 805, a de-scrambler 806 and a de-spreader 807. The receive filter 805 is configured to receive the signal D transmitted over the wireless transmission medium. The receive filter 805 filters the signal D and outputs a filtered signal E to the de-scrambler 806. The de-scrambler is configured to de-scramble the signal E by multiplying the signal E by a de-scrambling code to produce a de-scrambled signal. The de-scrambler 806 is also configured to insert zeros into the de-scrambled signal periodically. The position in the de-scrambled signal into which the zeros are inserted is determined by where zeros were in the original scrambled signal C, as described above in relation to Figure 6. The de-scrambler 806 outputs a signal F to the de-spreader 807. The de-spreader 807 is configured to receive the signal F and to multiply the signal F by de-spreading codes, as described above in relation to Figure 6. This results in m data streams G1 , G2... Gm being output from the de-spreader 807.

Figure 9 depicts only the transmitter portion of the system architecture described in relation to Figures 6 to 8 above. The transmitter comprises a duplicator 901 , a spreader

902, a scrambler 903 and a transmission filter 904. The duplicator 901 is configured to receive multiple data streams A1 , A2... Am and to output two copies of this incoming data stream i.e. to output A1 , A1 , A2, A2... Am, Am to the spreader 902. The spreader 902 is configured to receive the two copies of the data stream and to apply spreading codes to the data streams as described above in relation to Figure 6. The spread signals are summed together to form a signal B. The signal B is output by the spreader to a scrambler

903. The scrambler is configured to apply a scrambling code to the summed signal B by multiplying the summed signal B by the scrambling code. The scrambling code identifies the transmitter. The scrambler outputs a scrambled version of the spread signal B as a scrambled signal C to the transmission filter 904. The transmission filter filters the signal C and outputs a signal D for transmission over a wireless transmission medium.

Figure 10 depicts only the receiver portion of the system architecture described in relation to Figures 6 to 8 above. The receiver comprises a receive filter 1005, a de-scrambler 1006 and a de-spreader 1007. The receive filter 1005 is configured to receive the signal D transmitted over the wireless transmission medium. The receive filter 1005 filters the signal D and outputs a filtered signal E to the de-scrambler 1006. The de-scrambler is configured to de-scramble the signal E by multiplying the signal E by a de-scrambling code to produce a de-scrambled signal. The de-scrambler 1006 is also configured to insert zeros into the de-scrambled signal periodically. The position in the de-scrambled signal into which the zeros are inserted is determined by where zeros were inserted into the original scrambled signal C, as described above in relation to Figure 6. The de- scrambler 1006 outputs a signal F to the de-spreader 1007. The de-spreader 1007 is configured to receive the signal F and to multiply the signal F by de-spreading codes, as described above in relation to Figure 6. This results in m data streams G1 , G2... Gm being output from the de-spreader 1007.

In the example described above in relation to Figures 6 to 10, an aliased signal is generated in the spreader by manipulating the channelization codes such that every second bit in the scrambled signal is equal to zero. However, it is understood that every second bit in the scrambled signal can be forced to be zero by applying zero-forcing techniques to any or all of the following signals: all spreading codes, signal B, signal C or the scrambling code. For example, the "channelization codes" may be different to those described above (i.e. the codes used by the spreader to spread the data could have every other chip set to zero). Similarly, the transmitter may be configured to manipulate the signal at any point prior to the transmission in order to generate an aliased signal (i.e. to generate a signal having at least a portion of itself replicated within it).

Example receiver and transmitter architectures for aliasing the signal in other parts of the system than that described above in relation to Figures 6 to 10 are depicted in Figures 1 1 to 18 and described below.

Figure 1 1 depicts a transmitter configured to use a spreading code having periodically placed zeros to create an aliased scrambled signal B for inputting to a transmission filter. Figure 1 1 shows data streams A1 , A2... Am being input to spreader 1 101 . Only one copy of each of the data streams A1 , A2... Am are input to the spreader 1 101 . The spreader

1 101 is configured to mix each of the incoming data streams with a respective one of spreading codes SC1 1 . The spreading codes SC1 1 are formed using code generator

1 102 and zero forcer 1 103. The code generator 1 102 is configured to generate a subset of fundamental spreading codes, such as a subset of the channelization codes described in the UMTS/CDMA specification. In this context, the term fundamental spreading code is intended to indicate a spreading code specified by a particular standard or communication protocol. An example fundamental scrambling code for WCDMA UMTS is outlined below. The code generator 1 102 is configured to output the subset of fundamental spreading codes to the zero-forcer 1 103. The zero-forcer 1 103 is configured to manipulate the subset of fundamental spreading codes so as to output spreading codes SC1 1 having periodically zero-valued bits. The spreading codes SC1 1 are output by the zero-forcer to the spreader 1 101 . By multiplying each data stream by a spreading code SC1 1 having periodic zeroes, a spread signal is formed that is aliased. Once the spreader 1 101 has multiplied each incoming data stream by a respective one of the spreading codes SC1 1 , the multiplied signals are summed together to form a composite signal B1 1. Composite signal B1 1 is also aliased (i.e. composite signal B1 1 comprises at least one duplicate of a feature comprised within). The composite signal B1 1 is output to a scrambler 1 104. The scrambler 1 104 is configured to multiply the composite signal B1 1 by a scrambling code that identifies the transmitter to form a scrambled signal C1 1. As a result of the previous spreading operations, the scrambled signal C1 1 is aliased. The signal C1 1 is output to a transmission filter 1 105. The transmission filter is configured to filter the scrambled signal C1 1 to form a filtered signal D1 1 . The filtered signal D1 1 is output to a transmission element (not shown) for transmission over a wireless medium.

Another transmitter architecture is depicted in Figure 12. In Figure 12, the transmitter is configured to manipulate a spread signal prior to being scrambled so as to output a signal from the spreader having periodic zero-valued bits. The transmitter comprises a spreader 1201 configured to receive a plurality of data streams A1 , A2... Am. The spreader 1201 is configured to multiply each data stream with a respective spreading code. Once multiplied by a respective spreading code, the spread data streams are summed to form a composite signal B12'. The composite signal B12' is not aliased. The composite signal B12' is output to a zero forcer 1202. The zero forcer 1202 is configured to manipulate composite signal B12' so as to output an aliased spread signal B12 having periodically occurring zero-valued bits. The signal B12 is output by the zero forcer 1202 to the scrambler 1203. The scrambler 1203 is configured to receive the signal B12 and to multiply the signal B12 by a scrambling code that identifies the transmitter to form a scrambled signal C12. As a result of the previous zero forcing operation, the scrambled signal C12 is aliased. The signal C12 is output to a transmission filter 1205. The transmission filter is configured to filter the scrambled signal C12 to form a filtered signal D12. The filtered signal D12 is output to a transmission element (not shown) for transmission over a wireless medium.

Another transmitter architecture is depicted in Figure 13. In Figure 13, the scrambling code is configured to comprise periodic zeros. In Figure 13, a spreader 1301 is configured to receive multiple data streams A1 , A2... Am and to multiply each data stream by a respective spreading code. The multiplied signals are added together to form a composite signal B13. The composite signal B13 is not aliased. The composite signal B13 is output to a scrambler 1302. The scrambler 1302 is configured to multiply the composite signal B13 by a scrambling code SC13 that identifies the transmitter to form a scrambled signal C13. The scrambling code is formed using scrambling code generator 1303 and zero- forcer 1304. The scrambling code generator 1303 is configured to generate a fundamental scrambling code that identifies the transmitter. In this context, the term fundamental scrambling code is intended to indicate a scrambling code specified by a particular standard or communication protocol. An example fundamental scrambling code for WCDMA UMTS is outlined below. This generated fundamental scrambling code is output to the zero-forcer 1304 which is configured to periodically force certain bits of the generated fundamental scrambling code to zero in order to produce an aliased scrambling code SC13 that identifies the transmitter. The aliased scrambling code SC13 comprises a plurality of periodically occurring zero-valued bits. The scrambled signal C13 formed by multiplying the scrambling code SC13 and the composite signal B13 together is aliased as a result of the scrambling code SC13 being aliased. The scrambled signal C13 is output to a transmission filter 1305. The transmission filter 1305 filters the scrambled signal C13 to produce a signal D13 for transmission over a wireless medium by a transmission element (not shown).

Another transmitter is depicted in Figure 14. Figure 14 depicts a transmitter architecture in which a signal is aliased for transmission subsequent to the scrambling stage but prior to filtering by a transmission filter. In Figure 14, a spreader 1401 is configured to receive multiple data streams A1 , A2... Am and to multiply each data stream by a respective spreading code. The multiplied signals are added together to form a composite signal B14. The composite signal B14 is not aliased. The composite signal B14 is output to a scrambler 1402. The scrambler 1402 is configured to multiply the composite signal B14 by a scrambling code that identifies the transmitter to form a scrambled signal C14'. The scrambled signal C14' is not aliased. The scrambled signal C14' is output to a zero forcer 1403. The zero forcer 1403 is configured to manipulate the scrambled signal C14' to form an aliased spread and scrambled signal C14 comprising a plurality of periodically occurring zero-valued bits. The signal C14 is output by the zero forcer 1403 to a transmission filter 1404. The transmission filter 1404 is configured to filter the signal C14 to form a filtered signal D14 for transmission over a wireless medium by a transmission element (not shown). It is understood that, although in the example described above in relation to Figures 6 to

10, a signal is recovered in the receiver by recreating an aliased signal when de- scrambling the received filtered signal E, it is possible to recover the signal by recreating an aliased signal at other points in the receive chain. For example, every second bit of the de-spread signal can be forced to be zero in any or all of the following signals: all de- spreading codes, signal E, signal F and the de-scrambling code.

An example receiver architecture is depicted in Figure 15 in which the de-scrambler is configured to insert zeros into the received signal. The receiver of Figure 15 is configured to receive a signal D15 over a wireless medium and to input that signal to a receive filter 1501 . The receive filter 1501 filters the signal D15 to produce a filtered signal E15 that is output to a de-scrambler 1502. The de-scrambler is configured to multiply the filtered signal E15 by a de-scrambling code to produce a de-scrambled signal such that only every other bit value of the de-scrambled signal has a non-zero value. The de-scrambler 1502 outputs an aliased de-scrambled signal F15 to a de-spreader 1503. The de-spreader is configured to multiply the de-scrambled signal F15 by all of the de-spreading codes to produce two copies of m data streams G1 , G2... Gm. These two copies of the m data streams are output by the de-spreader to a discarder unit 1504. The discarder unit 1504 is configured to discard any one of the copies of the m data streams. Consequently, only one copy of data streams G1 , G2... Gm is output by the discarder unit 1504 for further processing by the receiver.

An example receiver architecture is depicted in Figure 16 in which neither the de- scrambler nor the de-spreader is configured to insert zeros into the received signal. The receiver of Figure 16 is configured to receive a signal D16 over a wireless medium and to input that signal to a receive filter 1601. The receive filter 1601 filters the signal D16 to produce a filtered signal E16 that is output to a de-scrambler 1602. The de-scrambler is configured to multiply the filtered signal E16 by a de-scrambling code to produce a de- scrambled signal. The de-scrambler 1602 outputs a de-scrambled signal F16 to a de- spreader 1603. The de-spreader is configured to multiply the de-scrambled signal F16 by all of the de-spreading codes C_ch,2ⁿ,k and C_ch,2ⁿ,k+2ⁿ-¹ (n≥1 , k = 0 ...2^n"1-1 ) as used in 603 to produce two copies of m data streams G1 , G2... Gm i.e. to produce G1 , G1 , G2, G2... Gm, Gm. These two copies of of the m data streams are de-spread versions of signal F16 and are output by the de-spreader to a combiner unit 1604. The combiner unit 1604 is configured to coherently combine matching pairs of signals in the two copies of the m data streams, resulting in G1 , G2... Gm. The m data streams G1 , G2... Gm are output by the de-spreader for further processing in the receiver.

Another receiver architecture is depicted in Figure 17. In Figure 17, the de-spreading code is configured to comprise periodic zeros for forcing the aliasing of the signals output by the de-spreader. The receiver of Figure 17 is configured to receive a signal D17 over a wireless medium and to input that signal to a receive filter 1701 . The receive filter 1701 filters the signal D17 to produce a filtered signal E17 that is output to a de-scrambler 1702. The de-scrambler is configured to multiply the filtered signal E17 by a de-scrambling code to produce a de-scrambled signal F17. The de-scrambled signal F17 is not aliased. The de-scrambled signal F17 is output to a de-spreader 1703. The de-spreader 1703 is configured to multiply the de-scrambled signal F17 by multiple de-spreading codes SC17 to produce m data streams G1 , G2... Gm. The de-spreading codes SC17 are formed using a spreading code generator 1704 and a zero-forcer 1705. The spreading code generator 1704 is configured to generate a subset of fundamental de-spreading codes for de-spreading the received signal. In this context, a fundamental de-spreading code is intended to indicate a de-spreading code specified by a particular standard or communication protocol. Only a subset of de-spreading codes are generated to avoid generating multiple copies of the data streams G1 , G2... Gm. The spreading code generator 1704 outputs the generated subset of fundamental de-spreading codes to zero- forcer 1705. The zero-forcer 1705 is configured to receive the generated subset of fundamental de-spreading codes and to create de-spreading codes SC17 comprising a plurality of periodically occurring zero-valued bits. The de-spreading codes SC17 are aliased. The m data streams G1 , G2... Gm are output by the de-spreader for further processing in the receiver.

Another receiver architecture is depicted in Figure 18. In Figure 18, the de-scrambling code is configured to comprise periodic zeros for forcing the aliasing of the signals output by the de-scrambler. The receiver of Figure 18 is configured to receive a signal D18 over a wireless medium and to input that signal to a receive filter 1801 . The receive filter 1801 filters the signal D18 to produce a filtered signal E18 that is output to a de-scrambler 1802. The de-scrambler is configured to multiply the filtered signal E18 by a de-scrambling code SC18 to produce a de-scrambled signal F18. The de-scrambling code SC18 is formed using a de-scrambling code generator 1804 and a zero-forcer 1805. The de-scrambling code generator 1804 is configured to generate a fundamental de-scrambling code for de- scrambling the received signal. In this context, a fundamental de-scrambling code is intended to indicate a de-scrambling code specified by a particular standard or communication protocol. The fundamental de-scrambling code identifies the transmitter of the received signal D18. The de-scrambling code generator 1804 outputs the generated de-scrambling code to zero-forcer 1805. The zero-forcer 1805 is configured to receive the generated de-scrambling code output a de-scrambling code SC18 having periodically inserted zero-value bits. The de-scrambling code SC18 is aliased. The de-scrambled signal F18 is aliased as a result of multiplying the filtered signal E18 with an aliased de- scrambling code SC18. The de-scrambled signal F18 is output to a de-spreader 1803. The de-spreader 1803 is configured to multiply the de-scrambled signal F18 by multiple de-spreading codes to produce m data streams G1 , G2... Gm. The m data streams G1 , G2... Gm are output by the de-spreader for further processing in the receiver. Regardless of which method is used (i.e. regardless of where the signal is aliased/zeros forced into the signal for passing through the transmission filter and/or to the receiver for further processing), the same data stream will appear after de-spreading for the signal F under the channelization codes C_ch,2ⁿ,k and C_ch,2ⁿ,k+2ⁿ-¹ (n≥1 , k = 0 ...2^n"1-1 ). This means that these two codes will always block each other and so should never be used simultaneously when the bandwidth is reduced by a half. Thus, it is noted that the above- described system reduces the throughput of the system by the factor of the bandwidth reduction. This is also why, in Figures 15 and 16, the receiver comprises either a combiner or a discarder for obtaining only one copy of each of the recovered data streams whilst Figures 17 and 18 utilise code subsets for obtaining only one copy of each data stream G1 , G2... Gm.

Processing of the received signal in the receiver may be performed using a RAKE receiver. A RAKE receiver is a receiver comprising multiple sub-receivers (called "fingers") for receiving on multiple frequency carriers. Each finger comprises a correlator configured to operate on a respective different frequency component. For simplicity, the following describes a possible process to be applied in a finger of a RAKE receiver configured to operate in accordance with the receiver embodiments described above in relation to Figures 6 to 18. Any processing of the received signal not mentioned below may be as per that applied in known RAKE receivers.

As mentioned above, when a de-scrambler in the receiver applies a de-scrambling code to the filtered input signal D, a de-scrambled signal F results. Signal F corresponds to the original signal B in the transmit chain. In this example, the signal F has been manipulated such that every second sample is forced to be zero in order to reconstruct the alias system components. As mentioned above, for de-spreading it is sufficient to use only a subset of the spreading codes C_ch,2ⁿ,k+2ⁿ-¹ (n≥1 , k = 0 ...2^n"1-1 ). Alternatively, the de- spreading can be performed using the complex conjugates of the opposed channelization codes used in the transmitter (e.g., using C_ch,2ⁿ,k and C_ch,2ⁿ,k+2ⁿ-¹ (n≥1 , k = 0 ...2^n"1-1 )). In this case, after de-spreading, any identical de-spread signals can be added coherently (as in the case of the receiver of Figure 16) to give an output signal G of the RAKE finger. The sample position of the RAKE receiver may be optimized to realize the forced zeroing of every other sample of the received signal. Using opposed channelization codes to force a zero into every second sample of the received signal, unwanted interference at the position of the zeroed samples may be removed from the received signal. The unwanted interference may be white noise, or other signal interference.

Further, the de-spreading can be realized by using only one code out of each set of the opposed channelization codes C_ch,2ⁿ,k and C_ch,2ⁿ,k+2ⁿ-¹ (n≥1 , k = 0 ...2^n"1-1 ) used by the transmitter. It doesn't matter which one of these codes is used to de-spread the signal when recovering a user signal G1 ... Gm. In this case, the de-spread signal G is output by the RAKE finger for further processing. The principles behind the example described above in relation to Figures 6 to 18 can be applied to other reductions of bandwidth, if the ratio constitutes a power of two. These principles can also be extended to when the available usable bandwidth is reduced by a larger factor. For example, assume the case where the useable carrier frequency bandwidth is a quarter of the frequency bandwidth of the spread signal. For example, for a transmit filter having a bandwidth of 0.96 MHz (i.e. a quarter of the bandwidth of the spread signal), four identical copies of the user data stream A1 , A2... Am are provided to the spreader. These four copies are each multiplied by four channelization codes that correspond to that data stream i.e. by the four channelization codes C_ch,2ⁿ,k, C_ch,2ⁿ,k+2ⁿ-²,

C_Ch,2ⁿ,k+2 2^n"2 and C_ch,2ⁿ,k+3 2^n"2 (n≥2, k = 0 ...2^n"2-1 ). This corresponds with a periodical appearance of three subsequent zero valued samples (i.e. Am(4, 0,0,0)) having a repeat period of every 4 samples. There is also a mutual spreading code blocking of the above four codes. This means that the number of data streams that can be conveyed at any one time is reduced by a factor of 1/4. In other words, the number of data streams that can be conveyed at any one time is modified by the fraction of actual bandwidth available for transmission by a device operating in accordance with a particular communication protocol over the maximum potential bandwidth usable by that transmitter in accordance with that communication protocol.

In general, a bandwidth reduction by the factor 2^r can be performed as follows: The 2^r channelization codes C_ch,2ⁿ,k, C_ch,2ⁿ,k₊2ⁿ-^r, C_ch,2ⁿ,k₊2-2ⁿ-^r, ■■■ C_ch,2ⁿ,k₊(2^r-i )-2ⁿ-^r (n≥r, k = 0 ...2^n"r-1 ) are to be added in step 1. This corresponds with a periodical appearance of 2^r-1 subsequent zero valued samples (period: 2^r samples) and a mutual spreading code blocking of the above 2^r codes. In some of the examples described above in relation to Figures 6 to 10, only a subset of spreading codes/de-spreading codes are used. In general, for de-spreading it is sufficient to use only the subset of the de-spreading codes C_ch,2ⁿ _,k (n≥1 , k = 0 ...2^n"1-1 ). In general, if the bandwidth is reduced by a factor of 1/2^r, the subset of spreading/de-spreading codes contains all the spreading/de-spreading codes from this bandwidth reduction that do not block each other. One example is a subset for a single de-spreading factor C_ch,2ⁿ _,k+_s 2ⁿ"^r (n≥r, k = 0 ...2^n"r-1 , s = 0 ... 2 ), wherein for each k only one value of s is allowed. The simplest utilization of this general system (which is as described above in relation to

Figures 6 to 18) is to set s=0, resulting in C_ch,2ⁿ _,k- The de-spreading code subset is the same as the spreading code subset for the transmitter. However, it is noted that the de- spreading code subset for the receiver may be a different spreading code subset for the transmitter. Alternatively, in any of the receiver architectures the full set of de-spreading codes can be used (such as described in relation to Figures 15 and 16). In these cases, as shown in Figures 15 and 16, the data belonging to blocked and hence unused codes is either discarded or combined coherently after de-spreading before they can be further processed by the receiver.

In the particular example outlined in relation to Figures 6 to 10, the identical data streams a_k in the spreader are combined using two different channelization codes having the relationship defined above. However, the summation of these identical data streams a_k can be carried out using a different set of signs. Thus, the combination

B^+" ₂,i = +A_k-Cch,2ⁿ,k - A_k-Cch,2ⁿ k₊2ⁿ-¹ = Ai -Cch,4,i - i -Cch,4,3 = Ai -(1 ,1 ,-1 ,-1 ) - Ai -(1 ,-1 ,-1 , 1 ) = ^^■(0,2,0,-2)

can be used instead. Using this combination (i.e. having different signs) results in a data offset compared to the example described above in relation to Figures 6 to 10. This affects the alignment of the spread signal B with the scrambling code. Though such generated signals are also aliased signals and so can also be used for transmission, problems from alignment with the scrambling code may appear with some receiver architectures if the data offset deviates from a default value. In this case, the spreading code or the application thereof may need to be modified.

The above mentioned principles are particularly advantageous when performed either during, immediately after or immediately before the scrambling operation. For example, for the receiver it is beneficial to periodically force zeros into the de-scrambling code at the receiver at a conversion of the signal from binary to real, either at the equation or after it when the sequence is formed.

As mentioned above in relation to the example of Figures 6 to 10 signal B (and hence signal C) is an aliased signal. If signal B (and hence signal C) were not an aliased signal, the relevant information from signal B would experience time varying gain. This is because the scrambling operation relocates the spectrum from signal B differently with respect to the channel filter(s). The effect of time varying gain is explained with relation to figures 19 to 22.

Figure 19 shows the power spectral density as a function of frequency of a random signal that is spread with the spreading code C_ch,2,o = (1 , 1 )- Because of the spreading, this spectrum is not flat, but rather a cosine shape having a maxima centred about OHz and crossing the frequency axis at +/-f_s/2 Hz. When scrambling is applied after spreading, each pair of spread samples experiences a multiplication with an individual section from the scrambling code, which may differ from another.

If the two corresponding samples of the scrambling code do not differ, the spectrum is not shifted. A filter with the full bandwidth from -f_s/2 to +f 2 will pass the full power of the signal. However, a filter with the bandwidth from -f_s/4 to +f_s/4 will only let a portion of the signal pass, in the case of the cosine shape in Figure 19 it will be 1/2 + 1/π = 81 ,8% of the full signal power. This is illustrated in Figure 20, which depicts the same cosine shape as Figure 19, but which includes cross-hatching to indicate the signal passed by the filter.

If the two corresponding samples of the scrambling code differ, the spectrum is shifted by f_s/2. A filter with the full bandwidth from -f_s/2 to +f_s/2 will still pass the full power of the signal. However, a filter with the bandwidth from -f_s/4 to +f_s/4 will let an even smaller portion of the signal pass. In the case of the cosine shape of Figure 19 it will be 1/2 - 1/π = 18,2% of the full signal power. This is illustrated in Figure 21 , which shows that the cosine shape has been shifted so that there is a minima centred at OHz and maxima at fs/2 Hz. Similar to Figure 20, Figure 21 comprises cross-hatching to illustrate the signal passed by the filter. Consequently, the signal gain varies in dependence on the scrambling code section. As illustrated in the above example, the time varying gain can differ by up to four and a half times (81.2/18.2), which is equivalent to 6.5 dB. Thus time varying gain can provide a significant effect on the transmitted signal. Also, though the gain values may differ, this effect also applies to all (and also longer) spreading codes (such as channelization codes).

Aliased signals, generated by zeroing out or grouping channelization codes, do not suffer in gain from frequency shifts by scrambling. This is shown by comparing Figures 7 and 22.

In Figure 22, there is depicted a graph having frequency (in Hertz) along the x-axis and power spectral density (in Watts per Hz) along the y-axis. The total spread signal is indicated by the numeral 2201. The total spread signal can be split up into two sections: a relevant data part (labelled as 2204 and 2205); and a redundant data part (labelled as 2206 and 2207). The relevant data part 2204 is identical to the redundant data part 2206. The relevant data part 2205 is identical to the redundant data part 2207. As the total signal comprises a replica of the relevant data parts 2204, 2205, the total signal may be described as being "aliased". The system has reduced usable bandwidth due, for example, to frequency/carrier re-farming. The bandwidth of the filter is centred around the centre of the reduced usable bandwidth "W" of the system. Figure 22 differs from Figure 7 only in that there has been a frequency shift of the total spread signal 2201 relative to Figure 7, such that the total signal is not centred about OHz. However, as seen in Figure 22, the movement out of the relevant data part 2204 on the left slope of the filter is compensated by the movement of the replica of part 2204 (i.e. by the redundant data part 2206) on the left slope. Hence, in this ideal example, no gain variation occurs.

There are more complicated methods to create an aliased signal C for inputting to a transmitter. One example is to fractionally delay signal C, which makes the periodic zeros disappear. However, even if the periodic zero valued samples do not appear in signal C, a periodic zero forcing as described above can be implemented as per the examples discussed above.

It is noted that any of any of the transmitter architectures described above in relation to Figures 6 to 18 can be configured to operate with any of the receiver architectures described above in relation to Figures 6 to 18. It is noted that although in the above described examples, the terms "transmitter" and "receiver" are employed, it is understood that these terms are used to denote an "apparatus configurable to be utilised within a transmitter" and an "apparatus configurable to be utilised within a receiver" respectively. This is to reflect the module-like nature of constructing communication devices, where different components may be manufactured by a different manufacturer to the manufacturer of the ultimate communication device.

In the above examples, the signal input into the transmit filter is aliased by periodically inserting zeros earlier in the transmit chain. Similarly the de-spread signal in the transmitter has been similarly aliased by periodically inserting zeros earlier in the receive chain. Both of these may be achieved via sampling. In this case, the zeros may be replaced with small valued samples (i.e. samples having a value of less than the mean value of the non-redundant part of the signal). However, the larger these samples are, the more error is introduced to the signal and the transmission quality is degraded. Thus zeros are preferred for creating an aliased signal.

In the above, particular reference is made to transmitting signals using wireless media. However, it is understood that the above described examples may be modified so as to transmit and receive signals using a wired medium.

It is noted that in all of the above mentioned embodiments, legacy hardware may be re- programmed to perform the steps described above. Thus the examples described above are backwards compatible with the previous system components. It is noted that in the above, the spread symbol rate has been set as 3.84MS/S. This is as this is the current rate prescribed by the 3GPP TS 25.213 protocol. However, it is understood that this value could change with time, or the above mentioned principles could be applied to other systems in which the bandwidth to be utilised for transmission is less than the bandwidth of the spread signal.

It is further noted that although the above described examples have used channelization codes as spreading codes, any code that increases the bandwidth of a signal when applied to that signal is suitable for use as a spreading code. In the following, we provide specific information from chapters 4.3.2 and 5.2.2 of 3GPP TS 25.213 that has particular relevant when the principles described above are applied to the system described therein. The scrambling codes are Gold sequences Z„, defined by:

Γ+ 1 if 7 (0 = 0

Z„ "( = 1 for i = 0,l, ... ,2²⁵ - 2.

- 1 if z_n (i) = l

The real-valued long scrambling sequences C|_0ng,i,n and C|_0ng,2,n , which are applied to message parts on a physical random access channel (PRACH) are defined as follows:

c_{ong n}(i) = Z_n(i), i = 0, 1 , 2, 2²⁵ - 2 and

Ciong,2,n( ) = Z_n((i + 16777232) modulo (2²⁵ - 1 )), / = 0, 1 , 2, ..., 2²⁵ - 2.

The complex-valued long scrambling sequence C|_{0ng, n>} is defined as:

C_long,n (i) = c_{long n} (i)(l + j(- 1)^! c_{long 2 n} 12j))

These binary sequences are converted to real valued sequences Z_n by the following transformation: Z„( = - 2.

The n:th complex scrambling code sequence S_di,_n is defined as:

- S_di,n(i) = Z_n(i) + j Z_n((i+131072) modulo (2¹⁸-1 )), i=0, 1 , ...,38399.

It is noted that, in the above, the terms "bit" and "sample" are used synonymously to indicate the value of a particular part of a code or signal.

The required data processing apparatus and functions of a control apparatus for the determinations at a communication device, a base station and any other node or element may be provided by means of one or more data processors. The described functions may be provided by separate processors or by an integrated processor. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non-limiting examples. The data processing may be distributed across several data processing modules. A data processor may be provided by means of, for example, at least one chip. Appropriate memory capacity can also be provided in the relevant devices. The memory or memories may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. An appropriately adapted computer program code product or products may be used for implementing the embodiments, when loaded or otherwise provided on an appropriate data processing apparatus, for example for causing determinations for adaptive assignment of retransmission transmission slot identities and for the related operations. The program code product for providing the operation may be stored on, provided and embodied by means of an appropriate carrier medium. An appropriate computer program can be embodied on a computer readable record medium. A possibility is to download the program code product via a data network. In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Embodiments of the inventions may thus be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate. It is noted that whilst embodiments have been described in relation to UMTS/WCDMA, similar principles can be applied to any other communication system where a carrier comprising a multiple of component carriers is employed. Therefore, although certain embodiments were described above by way of example with reference to certain exemplifying architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. For example, a combination of one or more of any of the other embodiments previously discussed can be provided. All such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims.

Claims

An apparatus comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to at least:

spread and scramble an input signal having a first bandwidth to form a spread signal having a second bandwidth, the second bandwidth being larger than the first bandwidth;

wherein the spread signal comprises a first part and a redundant part.

An apparatus according to claim 1 , the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to cause the transmission of at least the first part and no more than part of the redundant part.

An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to spread the input signal by applying a spreading code to the input signal, the spreading code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to spread the input signal by applying a spreading code to the input signal to form a first processed signal, and to subsequently manipulate the first processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to scramble the input signal by applying a scrambling code to the input signal, the scrambling code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

6. An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to scramble the input signal by applying a scrambling code to the input signal to form a second processed signal, and to subsequently manipulate the second processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the spread signal.

7. An apparatus according to any of claims 3 to 6 wherein, the predetermined feature is a zero.

8. An apparatus according to any of claims 3 to 7, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to repeat the predetermined signal periodically in the spread signal.

9. An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to form the redundant part of the spread signal such that it replicates at least part of the relevant part.

10. An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to filter the spread signal to form a filtered signal and to output the filtered signal for transmission.

1 1 . An apparatus according to claim 10, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to filter the spread signal using a filter bandwidth that is smaller than the second bandwidth.

12. An apparatus according to claim 10, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to filter the spread signal using a filter bandwidth that is smaller than the bandwidth of the first part.

13. An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to form the first part of the spread signal such that the first part has a smaller bandwidth than the second bandwidth.

14. An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to form the first part of the spread signal such that the first part has a smaller bandwidth than the second bandwidth.

15. An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to spread the input signal prior to scrambling the input signal.

16. An apparatus according to any preceding claim the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to scramble the signal by applying a scrambling code, the scrambling code being such that only every second bit has a non-zero value

17. An apparatus according to any of claims 1 to 15 the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to scramble the signal by applying a scrambling code, the scrambling code being such only one in four bits has a non-zero value.

18. An apparatus according to any of claims 16 and 17, wherein the non-zero values originate from a Gold code that identifies the apparatus and the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to form the scrambling code by sampling the Gold code.

19. An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to form the scrambling code using multiple repetitions of a scrambling code defined by a communication protocol,

20. An apparatus according to any preceding claim the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to spread the signal by applying a spreading code, the spreading code being such that only every second bit has a non-zero value

21 . An apparatus according to any of claims 1 to 18 the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to spread the signal by applying a spreading code, the spreading code being such only one in four bits has a non-zero value.

22. An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to form the spreading code using multiple repetitions of a spreading code defined by a communication protocol.

23. An apparatus according to any preceding claim, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to use only a subset of spreading codes from a plurality of spreading codes defined by a communication protocol for spreading the input signal.

24. A method comprising:

spreading and scrambling an input signal having a first bandwidth to form a spread signal having a second bandwidth, the second bandwidth being larger than the first bandwidth;

wherein the spread signal comprises a first part and a redundant part.

25. An apparatus comprising:

at least one processor; and

at least one memory including computer program code;

de-scramble and de-spread an input signal to form a de-spread signal; wherein the de-spread signal comprises a first part and a redundant part.

26. An apparatus according to claim 25 the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to insert the redundant part during at least one of the de-scramble, and the de-spread operations.

27. An apparatus according to any of claims 25 to 26, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to de-spread the input signal by applying a de-spreading code to the input signal, the de-spreading code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

28. An apparatus according to any of claims 25 to 27, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to de-spread the input signal by applying a de-spreading code to the input signal to form a first processed signal, and to subsequently manipulate the first processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

29. An apparatus according to any of claims 25 to 28, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to de-scramble the input signal by applying a de-scrambling code to the input signal, the de-scrambling code having a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

30. An apparatus according to any of claims 25 to 29, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to de-scramble the input signal by applying a de-scrambling code to the input signal to form a second processed signal, and to subsequently manipulate the second processed signal to have a predetermined feature, wherein the predetermined feature is configured to form at least part of the redundant part of the de-spread signal.

31 . An apparatus according to any of claims 27 to 30 wherein, the predetermined feature is a zero.

32. An apparatus according to any of claims 27 to 31 , the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to repeat the predetermined signal periodically in the de-spread signal.

33. An apparatus according to any of claims 25 to 32, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to form the redundant part of the de-spread signal such that it replicates at least part of the relevant part.

34. An apparatus according to any of claims 25 to 33, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to filter the input signal to form a filtered signal and to output the filtered signal for de-spreading and de-scrambling.

35. An apparatus according to any of claims 25 to 33, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to de-scramble the input signal prior to de-spreading the input signal.

36. An apparatus according to any of claims 25 to 35 the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to de-scramble the signal by applying a de-scrambling code, the de- scrambling code being such that only every second bit has a non-zero value

37. An apparatus according to any of claims 25 to 35 the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to de-scramble the signal by applying a de-scrambling code, the de- scrambling code being such only one in four bits has a non-zero value.

38. An apparatus according to any of claims 36 and 37, wherein the non-zero values originate from a Gold code that identifies the apparatus and the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to form the de-scrambling code by sampling the Gold code.

39. An apparatus according to any of claims 25 to 38, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to form the de-scrambling code using multiple repetitions of a de- scrambling code defined by a communication protocol.

40. An apparatus according to any of claims 25 to 39, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to de-spread the signal by applying a de-spreading code, the de- spreading code being such that only every second bit has a non-zero value

41 . An apparatus according to any of claims 25 to 39, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to de-spread the signal by applying a de-spreading code, the de- spreading code being such only one in four bits has a non-zero value.

42. An apparatus according to any of claims 25 to 41 , the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to form the de-spreading code using multiple repetitions of a de- spreading code defined by a communication protocol,

43. An apparatus according to any of claims 25 to 42, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to use only a subset of de-spreading codes from a plurality of de- spreading codes defined by a communication protocol for de-spreading the input signal.

44. A method comprising:

de-scrambling and de-spreading an input signal to form a de-spread signal, wherein the de-spread signal comprises a first part and a redundant part.

45. A system comprising:

the apparatus of claim 1 configured to cause the transmission of the relevant part to the spread signal; and

the apparatus of claim 25 configured to receive said transmission from the apparatus of claim 1 as an input signal for the de-scramble and de-spread.

46. A computer program comprising code means adapted to cause performing of the method of claim 24 when the program is run on data processing apparatus.

47. A computer program comprising code means adapted to cause performing of the method of claim 44 when the program is run on data processing apparatus.