GB2383721A

GB2383721A - A transmitter for a mobile communication system operable in more than one protocol

Info

Publication number: GB2383721A
Application number: GB0222526A
Authority: GB
Inventors: John Pope
Original assignee: INQUAM
Current assignee: INQUAM
Priority date: 2001-09-27
Filing date: 2002-09-27
Publication date: 2003-07-02
Also published as: GB2383700A; GB0123273D0; GB0222526D0; WO2003028395A1

Abstract

A terminal device for a mobile communication system is operable using more than one protocol eg CDMA,TDMA,FDMA,CDMA200,WCDMA. The switching between one protocol and another may involve band selection. The apparatus which makes this possible may be fitted to an existing mobile or base station.

Description

IMPROVEMENTS RELATING TO MOBILE COMMUNICATION SYSTEMS

The present invention relates to an apparatus and method for processing signals, and to a method of converting a mobile communication device or base station in 5 order to make efficient use of available bandwidth.

Conventional mobile communication systems employ a distributed array of base stations which each communicate with one or more mobile communication devices. The base stations and mobile devices communicate according to a 10 particular protocol, which typically employs a defined frequency band. In order to communicate with multiple devices, the base stations employ a suitable multiple-

access technique, such as time-domain-multiple access (TDMA), frequency-

domain-multiple-access (FDMA) or code-division-multiple-access (CDMA).

15 Some mobile devices are configured to enable them to communicate using a variety of different protocols and bands.

Occasionally new regions of the frequency spectrum become available, or new protocols are set. In order to exploit these new frequency bands or protocols, it is 20 necessary to install new networks and manufacture new mobile devices. This is an expensive solution, and thus it would be desirable to provide a means of adapting existing devices and/or base stations to exploit the new frequency bands/protocols. 25 A first aspect of the invention provides apparatus for processing a code-division-

multiplexed (CDMA) signal, the apparatus comprising a frequency converter for converting the CDMA signal between a first frequency band and at least a second frequency band.

30 The apparatus can be installed into an existing mobile communication device or base station, enabling the device/base station to communicate in a plurality of new frequency bands and bandwidths.

A The apparatus typically further comprises an amplifier for amplifying the CDMA signal before or after frequency conversion. The amplifier may be in the form of a linear amplifier. Instead, the amplifier may be in the form of a variable amplifier.

The apparatus may only convert in one direction (either uplink or downlink), but preferably comprises a first frequency converter for converting uplink signals; and a second frequency converter for converting downlink signals.

10 The apparatus may convert from/to any selected frequency band. In a preferred embodiment the first or second frequency band includes a frequency between 400 and 500 MHz.

A second aspect of the invention provides a mobile communication device 15 comprising an antenna for transmitting and/or receiving code-divisionmultiplexed (CDMA) signals via a wireless communication medium; and apparatus according to the first aspect of the invention for frequency converting the CDMA signals.

A third aspect of the invention provides a base station comprising an antenna for 20 transmitting and/or receiving code-division-multiplexed (CDMA) signals via a wireless communication medium; and apparatus according to the first aspect of the invention for frequency converting the CDMA signals.

A fourth aspect of the invention provides a communication system comprising one 25 or more mobile communication devices according to the second aspect of the invention; and one or more base stations according to third aspect of the invention.

A fifth aspect of the invention provides a method of converting apparatus configured to transmit and/or receive code-division-multiplexed (CDMA) signals in 30 a first frequency band via a wireless communication medium, the method comprising installing a frequency converter to convert the CDMA signals between the first frequency band and at least a second frequency band.

/ - 3 A sixth aspect of the invention provides a method of converting a code-division-

multiplexed (CDMA) signal, the method comprising converting the COMA signal between a first frequency band and at least a second frequency band.

5 A seventh aspect of the invention provides a mobile communication device comprising an antenna for transmitting and/or receiving signals via a wireless communication medium; and a frequency converter for converting the signals between a first frequency band and at least a second frequency band.

10 The seventh aspect of the invention provides a mobile device which can communicate in a variety of protocols, including TDMA, FDMA and COMA.

An eighth aspect of the invention provides a communication system comprising one or more mobile communication devices according to the seventh aspect of the 15 invention; and one or more base stations, each base station comprising an antenna for transmitting and/or receiving signals via a wireless communication medium, and a frequency converter for converting the signals between a first frequency band and at least a second frequency band.

20 A ninth aspect of the invention provides a method of converting a mobile communication device configured to transmit and/or receive signals in a first frequency band via a wireless communication medium, the method comprising installing a frequency converter into the device to convert the signals between the first frequency band and at least a second frequency band.

A tenth aspect of the invention provides a method of transmitting a signal from a mobile communication device, the method comprising generating a signal in a first frequency band, converting the signal into at least a second frequency band, and transmitting the converted signal from the mobile communication device.

An eleventh aspect of the invention provides a method of processing a signal at a mobile communication device, the method comprising receiving a signal in a first

- 4 - frequency band at the mobile communication device, and converting the signal at the mobile communication device into at least a second frequency band.

According to another aspect of the invention, there is provided apparatus for a 5 communication system including transceiver equipment, said apparatus comprising means (preferably in the form of a processor which may form part of the transceiver equipment, or a software module) for generating a signal for transmission in accordance with a given communication protocol, said generating means further being arranged to generate a signal for transmission in accordance 10 with at least one further communication protocol.

Preferably, the apparatus further comprises means (preferably in the form of a processor which may form part of the transceiver equipment, or a software module) for frequency shifting the signal for transmission in the frequency domain 15 prior to transmission.

In preferred examples, the term communication protocol preferably refers to multiple-access air interface technologies, such as for example, COMA, FDMA and TDMA, and different 3G mobile communications multiple-access protocols 20 such as CDMA2000 and WCDMA.

The possibility of utilizing a variety of communication protocols together with any possible frequency band provides increased flexibility, as it is possible to utilize a variety of different protocols together with available frequency spectrum.

Preferably, the apparatus further comprising means for selecting a communication protocol to be used for generating the signal for transmission.

Preferably, the communication protocol selecting means is arranged to select the communication protocol to be used for generating the signal on the basis of a 30 characteristic of the communication system.

Preferably, the characteristic may relate to network capacity.

- 5 Also, preferably the characteristic may relate to subscriber requirements. The characteristic may also relate to other performance characteristics, for example relating to maximizing data rate transfer.

Preferably, the apparatus further comprises means for selecting a frequency shift factor to be used for frequency shifting the signal for transmission.

Preferably, the frequency shift factor selecting means is arranged to select the 10 frequency shift factor on the basis of a network characteristic.

Also preferably, the characteristic may relate to frequency spectrum availability.

Preferably, the apparatus may further comprise means for storing the 15 communication protocol selection.

Preferably, the apparatus further comprises means for storing a frequency shift factor. 20 Preferably, the apparatus further comprises means for receiving a control signal and means for controlling said generating means and/or said frequency shifting means in accordance with the control signal.

Preferably, the generating means comprises first generating means for generating 25 uplink signals and second generating means for generating downlink signals.

Preferably, the apparatus further comprises first frequency shift means for frequency shifting uplink signals and second frequency shift means for frequency shifting downlink signals.

Preferably, the generating means is arranged for selectively alternating between generating the signal for transmission in accordance with each of the

-6 communication protocols. In this way it is possible to change protocols as and when required, based on network capacity and subscriber requirements, for example, thereby providing increased agility.

5 Preferably, the apparatus further comprises means for converting a signal between a form suitable for transmission using a first communication protocol and at least a second communication protocol.

Preferably, the frequency shifting means is arranged for selectively alternating 10 between shifting the signal for transmission in the frequency domain in accordance with a plurality of frequency shift factors. Similarly, in this way it is possible to change the frequency band used as and when required, based on spectrum availability, thereby providing increased agility.

15 According to a further aspect of the invention, there is provided a mobile communication device comprising, an antenna for transmitting and/or receiving signals via a wireless communications medium and apparatus as hereinbefore described. 20 According to another aspect of the invention, there is provided an antenna for transmitting and receiving signals via a wireless communications medium to a plurality of mobile communications devices and apparatus as hereinbefore described. 25 Preferably, the term radio access network device refers to devices forming part of the radio access network of a mobile of wireless communications network, such as for example, a base station controller (BSC) or base transceiver station (BTS).

Furthermore, the term radio access should preferably not be considered to be restricted to a system using any particular wavelength of radiation, but rather to 30 refer to, as appropriate, any form of electromagnetic radiation, for example microwaves or infrared waves.

r - 7 According to a further aspect of the invention, there is provided a communications system comprising one or more mobile communications devices as hereinbefore described and one or more radio access network devices as hereinbefore described. Preferably, the communications system further comprises means for comparing a plurality of switching centers thereby to determine a characteristic of each switching center and means for controlling said generating means and/or said frequency shifting means in response thereto.

Preferably, the characteristic may relate to network capacity and/or to subscriber requirements. Preferably, the communications system may further comprise means for 15 determining frequency spectrum availability in at least part of the communications system and means for controlling said frequency shifting means in response thereto. This can provide the advantage of increased quality of service delivered by the 20 network to the subscribers. Furthermore, the protocols and frequency bands used are preferably transparently implemented by the radio access network and mobile telephones. Preferably, at least one of the radio access network devices is arranged to 25 communicate with a conventional mobile communication device.

According to another aspect, the invention provides apparatus for a communication system including transceiver equipment, said apparatus comprising means for outputting a signal suitable for transmission using a given 30 communication protocol, said outputting means further being capable of outputting a signal suitable for transmission using a different communication protocol.

- 8 In another aspect, the invention provides a method of operating a radio access network device, which comprises generating a signal for transmission in accordance with a given communication protocol, said generating means further being arranged to generate a signal for transmission in accordance with at least 5 one further communication protocol.

According to another aspect of the invention, there is provided a method of operating a radio access device, which comprises converting a signal between a form suitable for transmission using a first communication protocol and at least a 10 second communication protocol.

According to a further aspect, the invention provides a method of operating a mobile communication device, which comprises generating a signal for transmission in accordance with a given communication protocol, said generating 15 means further being arranged to generate a signal for transmission in accordance with at least one further communication protocol.

According to yet a further aspect, the invention provides a method of operating a mobile communication device, which comprises converting a signal between a 20 form suitable for transmission using a first communication protocol and at least a second communication protocol.

According to another aspect of the invention, there is provided apparatus for a communication system including transceiver equipment, said apparatus 25 comprising means for frequency shifting a signal in the frequency domain, said signal having been generated for transmission in accordance with a given communication protocol, and comprising means for selecting a frequency shift factor to be used for frequency shifting the signal.

30 As mentioned, in preferred examples, the term communication protocol refers to multiple-access air interface technologies, such as for example, COMA, FDMA and TDMA, and different 3G mobile communications multipleaccess protocols

- 9 - such as CDMA2000 and WCDMA.

The apparatus can be installed into an existing mobile communication device or 5 radio network access device, thereby enabling the devices to communicate using different bands or bandwidths of the available frequency spectrum, thereby providing increased flexibility and improving network capacity.

In one embodiment the given communication protocol is a code division multiple 10 access (CDMA) communication protocol.

According to another aspect, the invention provides apparatus for a communication system including transceiver equipment, said apparatus comprising means for frequency shifting a signal in the frequency domain, said 15 signal having been generated for transmission in accordance with a code division multiple access (COMA) communication protocol, and comprising means for selecting a frequency shift factor to be used for frequency shifting the signal.

Preferably, the apparatus further comprises means for receiving a control signal 20 and means for controlling said frequency shifting means in accordance with the control signal.

Preferably, the frequency shift factor selecting means is arranged to select the frequency shift factor on the basis of a network characteristic.

Preferably, the characteristic may relate to frequency spectrum availability.

Preferably, the frequency shifting means is arranged for alternatively shifting the signal for transmission in the frequency domain in accordance with a plurality of 30 frequency shift factors.

Thus it is possible to use any available frequency band and to shift between

- 10 different bands dynamically depending on frequency spectrum availability.

Preferably, the apparatus further comprises an amplifier for amplifying the signal before or after frequency conversion.

In one embodiment, the amplifier is in the form of a linear amplifier.

In another embodiment the amplifier is in the form of a variable amplifier.

10 Preferably, the frequency shifting means comprises a first frequency converter for converting uplink signals and a second frequency converter for converting downlink signals.

According to another aspect of the invention, there is provided a mobile 15 communication device comprising an antenna for transmitting and/or receiving signals via a wireless communication medium; and apparatus as hereinbefore described for shifting the signal in the frequency domain.

According to yet another aspect of the invention, there is provided a base station 20 comprising an antenna for transmitting and/or receiving signals via a wireless communication medium; and apparatus as hereinbefore described for frequency converting the signals.

According to another aspect of the invention, there is provided a communication 25 system comprising one or more mobile communication devices as hereinbefore described and one or more base stations as hereinbefore described.

According to another aspect of the invention, there is provided a method of converting apparatus configured to transmit and/or receive signals in a first 30 frequency band via a wireless communication medium, the method comprising installing apparatus as hereinbefore described for shifting the signal in the frequency domain to at least one further frequency band.

- 11 According to yet another aspect, the invention provides a method of converting a code-division-multiplexed (COMA) signal, the method comprising converting the COMA signal between a first frequency band and at least a second frequency 5 band.

According to another aspect, the invention provides a mobile communication device comprising an antenna for transmitting and/or receiving signals via a wireless communication medium; a frequency converter for converting the signals 10 between a first frequency band and at least a second frequency band and means for selecting a frequency shift factor used for the frequency conversion.

Also preferably, the characteristic relates to frequency spectrum availability.

Preferably, the device further comprises means for receiving a control signal and means for controlling said frequency shifting means in accordance with the control 20 signal.

Preferably, the device further comprises an amplifier for amplifying the signals before or after frequency conversion.

Preferably, the device further comprises a first frequency converter for converting uplink signals; and a second frequency converter for converting downlink signals.

In one embodiment, the first or second frequency band includes a frequency 30 between 400 and 500 MHz.

According to another aspect of the invention, there is provided a communication

- 12 system comprising one or more mobile communication devices as hereinbefore described; and one or more base stations, each base station comprising an antenna for transmitting and/or receiving signals via a wireless communication medium, and a frequency converter for converting the signals between a first 5 frequency band and at least a second frequency band and comprising means for selecting a frequency shift factor used for the frequency conversion.

According to another aspect of the invention, there is provided a method of converting a mobile communication device configured to transmit and/or receive 10 signals in a first frequency band via a wireless communication medium, the method comprising installing a frequency converter into the device to convert the signals between the first frequency band and at least a second frequency band, said frequency converter comprising means for selecting a frequency shift factor used for the frequency conversion.

According to another aspect of the invention, there is provided a method of transmitting a signal from a mobile communication device, the method comprising generating a signal in a first frequency band, selecting a frequency factor to be used for converting the signal to at least a second frequency band on the basis of 20 a network characteristic, converting the signal into at least a second frequency band, and transmitting the converted signal from the mobile communication device. According to another aspect of the invention, there is provided a method of 25 processing a signal at a mobile communication device, the method comprising receiving a signal in a first frequency band at the mobile communication device, and converting the signal at the mobile communication device into at least a second frequency band.

30 An embodiment of the invention will now be described with reference to the accompanying drawings, in which:

- 1 3 Figure 1 is a schematic diagram of a 3G mobile telephone system; Figure 2 is a detailed view of a mobile telephone; 5 Figure 3 is a detailed view of a base station; Figure 4 is a schematic diagram of part of a mobile communications network; and Figure 5a and 5b show schematic diagrams of possible methods of spreading 10 access protocols over the frequency spectrum.

Referring to Figure 1, a 3G mobile telephone system comprises a network 1 coupled to a plurality of base stations 2. Each base station 2 communicates with one or more mobile telephones 5 via a wireless transmission medium.

The network 1 and base stations 5 are configured to communicate according to any CDMA Band Class, such as, for example, Band Class 1 (North American PCS Band), which operates at approximately 1900 MHz. Further details relating to this Band Class, as well as the other CDMA Band Classes and Standards are 20 available in the relevant CDMA Standards Document, TIA/EIA/IS-2000.2--1.

Each mobile telephone 5 transmits uplink signals on a selected one of the CDMA channels provided by Band Class 1. For instance, a mobile telephone may transmit on channel 300, which occupies the 1865 - 1866.2 MHz frequency band.

25 The base station 2 transmits downlink signals to that mobile telephone on channel 300, which in this case occupies the 1945 -1946.2 MHz frequency band.

One of the mobile telephones 5 is shown in detail in Figure 2. Antenna 10 receives and transmits downlink/uplink signals and is coupled to a 30 converter/repeater designated generally at 20. The converter/repeater 20 comprises a duplexer 21 which receives downlink signals from the antenna 10 and passes them to a downlink signal processing arm designated generally at 30. The

- 14 duplexer 21 also receives uplink signals from an uplink arm designated generally at 40 and passes them on to the antenna 10 for transmission.

The downlink arm 30 comprises a low noise amplifier 31, mixer 32, frequency 5 generator 33, band pass filter 34, and power amplifier 35. The low noise amplifier 31 is optional, but is particularly useful in operations involving a high power forward link. The mixer 32 receives downlink signals in a first frequency band and converts them to a second frequency band in accordance with the signal from frequency generator 33. The band pass filter 34 passes signals in the second 10 frequency band. The power amplifier 35 is selectable for low and high power applications, and in some embodiments incorporates an automatic gain control circuit to ensure the converter/repeater 20 does not go into oscillation.

The uplink arm 40 comprises a variable amplifier 41 (incorporating an automatic 15 gain control circuit), band pass filter 42, mixer 43 and frequency generator 44.

These components operate in a similar manner to the equivalent components in the downlink arm 30.

The downlink/uplink arms 30,40 are coupled to a second duplexer 50 which is 20 coupled in turn to a processor 51. The processor 51 receives the downlink signals and outputs corresponding output signals to an output stage 52 (for example comprising a loudspeaker and/or display screen). The processor also receives input signals from an input stage 53 (for example comprising a microphone and/or keyboard) and outputs corresponding uplink signals to the duplexer 50.

One of the base stations 2 is shown in detail in Figure 3. The components of base station 2 are similar to the components of mobile telephone 5, and equivalent components are given corresponding reference numerals. Thus for example base station downlink arm 40' is equivalent to mobile telephone uplink arm 40, etc. The 30 only structural difference between the mobile telephone converter/repeater 20 and the base station converter/repeater 20' is that there is an additional channel

- 15 between amplifier 35' and duplexer 50' in order to support receive diversity for range enhancement.

The duplexer 50' is coupled to a base transceiver station (BTS) 60, which is 5 coupled in turn to network 1.

In the preferred embodiment, the mobile network 1 includes equipment configured to operate using CDMA Band Class 1 (North American PCS); thus the mobile telephone processor 51 and BTS 60 are configured to process signals in this 10 band. However, the converter/repeaters 20 located in the mobile telephones used, as well as the converter/repeaters 20' connected to each BTS 60, enable use at any CDMA band, such as CDMA Band Class 5 (NMT-450 Band). Note that if the "Do Block is used in Band Class 1, then the defined block size is 5MHz, which corresponds to the 5MHz block defined for CDMA Band Class 5 (see 15 TIA/EIAJIS-2000.2-1 for further details).

Thus, the BTS outputs downlink signals corresponding to Band Class 1, and the mobile telephone outputs unlink signals corresponding to Band Class 1, and the respective converter/repeaters 20'20 convert these signals to Band Class 4.

More specifically, BTS 60 signals to the frequency generators 33' 44' and band pass filters 34' 42' the specific frequency at which the base station is operating, corresponding to a particular designated channel in Band Class 1, and sets the frequency generators 33'44'to appropriate frequencies relevant for Band Class 4.

25 Similarly, band pass filters 34' 42' are set to frequencies surrounding the appropriate frequency used in Band Class 4.

It is also possible to isolate the BTS 60 from the converter/repeater 20'. In this case, the BTS 60 is not directly connected to the frequency generators and band 30 pass filters in the uplink and downlink signal processing arms respectively, and the frequency generators and band pass filters are pre-programmed, for example by

- 16 an operator. Thus, the BTS 60 does not need be aware of the frequency used by the converter/repeater 20'.

Similarly, at the mobile telephone end, processor 51 signals to the frequency 5 generators 33 44 and band pass filters 34 42 that the base station is currently transmitting and receiving on a specific designated channel in Band Class 1. The processor then sets frequency generators 33 44 and band pass filters 34 42 to an appropriate frequency in Band Class 4.

10 It is also possible to isolate the processor 51, of the mobile telephone, from the converter/repeater 20. However, the provision of a link between the processor 51, and the frequency generating at the converter/repeater 20, enables the mobile telephone to dynamically alter the frequency band at which it operates, thereby providing bandwidth agility.

It is also envisaged that the converter/repeater 20 may be configured to convert from a first frequency band to multiple frequency bands, thereby enabling the use of multiple available bands.

20 The converter/repeaters 20' 20 are able to convert any standard CDMA equipment and allow it to operate in the 450 MHz band, or any other desired frequency band.

The converter/repeaters 20' 20 support a variety of media includingdigital fibre, digital microwave, cable or off air connections to the BTS. Various inpuVoutput options for the 450MHz Band Class 5 include: 850 MHz CDMA w/5 MHz block defined 1900 MHz CDMA w/5 MHz block defined 30 450 MHz CDMA w/5 MHz block defined Baseband or Fiber Optic Digital Output w/5 MHz block defined

- 17 Microwave Output wt5 MHz block defined However, it is important to note that any defined CDMA Band or Block could be used. The converter/repeaters 20' 20 may be installed as a modular component. They have a characteristic impedance of 50 Ohms, a noise figure of < 5dB, a group delay < 5 microseconds, a passband ripple < 3dB pep, Rho of > 95% (BTS and converter/repeater must comply with the appropriate IS-97 standard as a 10 minimum) and VSWR < 1.5:1. Spurious emissions comply with ANSI J-008 as a minimum. The standards applicable to the handset side physical performance are specified in the appropriate sections of IS- 98. IS-97 is specific to the BTS components.

The converter/repeater 20' may also be configured with alarming capabilities using a redundant path (not shown) to the BTS 60.

Further aspects of the invention are now described with reference to an 20 embodiment of the invention illustrated in Figures 4 and 5a and 5b of the drawings. As mentioned above the converter/repeaters 20 20' can be used together with a variety of different protocols or air interface access technologies. As mentioned a 25 number of common multiple access technologies are FDMA, TDMA and CDMA.

Typically, FDMA techniques are employed in first generation (1 G) mobile networks, TDMA and CDMA techniques are used in second generation (2G) mobile networks and CDMA2000 and Wideband CDMA (WCDMA) protocols are used in third generation (3G) networks. There are also various intermediate or 30 migration technologies which lie somewhere between 2G and 3G - so called 2.5G technologies, such as GPRS and CDMA2000-1X.

- 18 By way of background, CDMA2000 is a multi-carrier technology, which has a

number of different forms, some of which are at present available, and others which are still under development. CDMA2000-1X uses a 1.25 MHz bandwidth, like existing 2G CDMA systems, however this platform provides increased 5 capacity due to a higher coding scheme. CDMA2000 also incorporates 1xEV-DO and 1xEV-DV, data only and voice only carriers respectively. Fully-fledged 3G access will be provided by CDMA-3X which will use 3 bands of 1.25 MHz each.

WCDMA is a 3G access technology which supports the Universal Mobile Telecommunications Service (UMTS) platform, which represents an evolution from 10 GSM, and utilises a single 5 MHz band.

Figure 4 shows a network 71 where different access technologies are provided by a single service provider or network operator, or by different service providers or operators. In this embodiment, the base station controller (BSC) and base 15 transceiver station (BTS) 60 are represented by radio access network 70 which is shown connected to the converter/repeater 20'. The FRAN 70 is also connected via an Internet protocol (IP) link 72 and a CODEC (coder/decoder) 74 to various switches supporting different access technologies or protocols. For example, a Universal Mobile Telecommunications Service (UMTS) switch 78, a CDMA switch 20 80 and an FDMA switch 82 are shown. A master switch 76 provides an interface between these switches 78 80 82. The switches 78 80 82 are also connected via a data gateway 84 to the Internet 86, which is in turn connected to other communications networks.

25 The RAN 70 is also provided with means for converting or modifying a signal for transmission in accordance with any one of a plurality of multi-access protocols, in the form of a protocol selector 88, which enables the RAN 70 to use a number of different protocols, for example, UMTS, CDMA and FDMA, and associated processors 90, 92 and 94, each for handling transmission using UMTS, CDMA 30 and FDMA respectively. These are each connected to the converter/repeater 20'.

- 19 ln this embodiment, the mobile telephone or handset 5 (not shown in Figure 4) is also provided with similar functionality to that of the RAN 70, and in addition to a converter/repeater 20 it is also provided with software and or additional processing capability to enable it to handle reception and transmission using different air 5 interface access technologies or protocols.

In order to allow the network 71 to operate using any number of different protocols or at a variety of frequencies, rule-based selection techniques are used to select an appropriate air interface access protocol. Thus, when a new mobile telephone 10 5 enters a particular cell or sector covered by a particular BTS 60, the RAN 70 communicates this to the master switch 76 which, based on various criteria, such as the capacity of the switches 78 80 and 82, determines which protocol the mobile telephone 5 should use. This information is then communicated to the RAN via the IP link 72, in the form of a control signal. The RAN then allocates 15 resources using a particular protocol and the mobile telephone 5 is assigned to a channel supporting that protocol. The connection would be verified complete when the appropriate channel and switch resources are verified to the mobile telephone 5.

20 In another embodiment, the network may in addition allow equipment designed to operate using a specific communication protocol to use any other communication protocol. For example, a mobile telephone designed to operate using CDMA2000 could be used in the network and operates using any protocol specified by the network. In this case, an additional software module or processor (not shown) is 25 incorporated into the protocol selector 88 which enables it to convert from one protocol to another. In an embodiment, for example, this module or processor could allow conversion between say COMA and FDMA, by compressing baseband COMA information and then transmitting it over an FDMA channel.

30 As mentioned, the allocation of resources by the network 71 may be based on a number of different criteria. In one embodiment, the criteria could be to provide the maximum possible data rate to each subscriber. In another embodiment the

- 20 criteria may be to maximize the capacity in a particular cell or sector. This results in the network being able to allocate resources more effectively thereby increasing performance. 5 The above protocol or access technology flexibility is provided together with the frequency agility provided by the converter/repeater 20' which allows the RAN 70 to allocate available bandwidth or bands to the mobile telephone 5. Thus, for example, the BTS 60 and mobile telephone 5 might communicate using any of a number of bands or protocols available, depending on bandwidth availability and 10 which protocols are provided. In this way the network 71 provides both frequency, technology and/or protocol agility.

In one embodiment the network 71 is also frequency and technology agnostic in which case the frequencies and access protocols used by the mobile telephone 5 15 and respective BTS 60 are transparent to the mobile telephone 5 and BTS 60.

Thus, mobile communications equipment and mobile telephones are able to use any frequency or access technology available, which maximises the efficiency of the air interface.

20 In this case, the control signal containing information about which frequency and protocol to allocate to a particular mobile telephone 5 may be passed directly to the frequency selector 88 and the converter/repeater 20' which then interfaces with the corresponding repeater/converter 20 and frequency selector in the mobile telephone 5 in order to set up the communication channel. Thus, the mobile 25 telephone 5 and BTS 60 are agnostic to the frequency band and interface protocols used for communication.

It should be noted that although different access technologies are typically allocated different frequency bands, as shown in the frequency spectrum diagram 30 in Figure 5a, due to the different orthogonal coding schemes used by different technologies, for example CDMA2000-1X and UMTS, it is possible for both to be allocated overlapping portions of the spectrum, as shown in the frequency

: - 21 spectrum diagram in Figure fib. Thus, it is possible that the converter/repeater 20' could allocate the same portion of the spectrum to subscribers using different protocols. This further increases the flexibility and efficiency of the system. This is in general only possible if a certain amount of performance degradation can be 5 tolerated.

It is also possible to make use of partial channels. Since baseband information flow is controlled it is possible to transmit voice using one protocol and data using another. Thus, for example, different bearer channels or B-channels could be 10 supported using different protocols orfrequencies.

In another embodiment, the converter/repeater 20' may be incorporated into a Software Defined Radio (SDR) network. SDR allows channel modulation waveforms to be defined in software. Thus software is used to determine a 15 modulation technique or air interface technology. Thus, in an SDR network, different protocols or access technologies can be used to maximize efficiency.

The converter/repeater 20' extends this by allowing flexibility with respect to frequency, thus providing the ability to use different bands and bandwidths or, in fact, all frequency space (in the case of ultra wide band). Thus an SDR network 20 incorporating the converter/repeater 20' 20 will provide both technology flexibility and frequency flexibility.

It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of 25 the invention.

Each feature disclosed in the description, and (where appropriate) the claims and

drawings may be provided independently or in any appropriate combination.

30 The invention also provides a computer program and a computer program product for carrying out any of the methods described herein and/or for embodying any of the apparatus features described herein, and a computer readable medium having

- 22 stored thereon a program for carrying out any of the methods described herein and/or for embodying any of the apparatus features described herein.

The invention also provides a signal embodying a computer program for carrying 5 out any of the methods described herein and/or for embodying any of the apparatus features described herein, a method of transmitting such a signal, and a computer product having an operating system which supports a computer program for carrying out any of the methods described herein and/or for embodying any of the apparatus features described herein.

The invention extends to methods and/or apparatus substantially as herein described with reference to the accompanying drawings.

Any feature in one aspect of the invention may be applied to other aspects of the 15 invention, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa.

Features implemented in hardware may generally be implemented in software, and vice versa. Any references to software and hardware features herein should 20 be construed accordingly.

Reference numerals appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.

Claims

- 23 CLAIMS

1. Apparatus for a communication system including transceiver equipment, said apparatus comprising means for generating a signal for 5 transmission in accordance with a given communication protocol, said generating means further being arranged to generate a signal for transmission in accordance with at least one further communication protocol.

2. Apparatus according to claim 1, further comprising means for 10 frequency shifting the signal for transmission in the frequency domain prior to transmission.

3. Apparatus according to any of the preceding claims, further comprising means for selecting a communication protocol to be used for 15 generating the signal for transmission.

4. Apparatus according to claim 3, wherein the communication protocol selecting means is arranged to select the communication protocol to be used for generating the signal on the basis of a characteristic of the communication 20 system.

5. Apparatus according to claim 4, wherein the characteristic relates to network capacity.

25

6. Apparatus according to claim 4, wherein the characteristic relates to subscriber requirements.

7. Apparatus according to any of the preceding claims, further comprising means for selecting a frequency shift factor to be used for 30 frequency shifting the signal for transmission.

8. Apparatus according to claim 7, wherein the frequency shift factor

- 24 selecting means is arranged to select the frequency shift factor on the basis of a network characteristic.

9. Apparatus according to claim 7, wherein the characteristic relates to 5 frequency spectrum availability.

10. Apparatus according to any of the preceding claims, further comprising means for storing the communication protocol selection.

10

11. Apparatus according to any of the preceding claims, further comprising means for storing a frequency shift factor.

12. Apparatus according to any of the preceding claims, further comprising means for receiving a control signal and means for controlling said 15 generating means and/or said frequency shifting means in accordance with the control signal.

13. Apparatus according to any of the preceding claims, wherein the generating means comprises first generating means for generating uplink 20 signals and second generating means for generating downlink signals.

14. Apparatus according to any of the preceding claims, further comprising first frequency shift means for frequency shifting uplink signals and second frequency shift means for frequency shifting downlink signals.

15. Apparatus according to any of the preceding claims, wherein the generating means is arranged for selectively alternating between generating the signal for transmission in accordance with each of the communication protocols.

16. Apparatus according to any of the preceding claims, further comprising means for converting a signal between a form suitable for

- 25 transmission using a first communication protocol and at least a second communication protocol.

17. Apparatus according to any of the preceding claims, wherein the 5 frequency shifting means is arranged for selectively alternating between shifting the signal for transmission in the frequency domain in accordance with a plurality of frequency shift factors.

18. A mobile communication device comprising, an antenna for 10 transmitting and/or receiving signals via a wireless communications medium and apparatus according to any of the preceding claims.

19. A radio access network device comprising, an antenna for transmitting and receiving signals via a wireless communications medium to a 15 plurality of mobile communications devices and apparatus according to any of the preceding claims 1 to 18.

20. A communications system comprising one or more mobile communications devices according to claim 18 and one or more radio access 20 network devices according to claim 19.

21. A communications system according to claim 20, further comprising means for comparing a plurality of switching centers thereby to determine a characteristic of each switching center and means for controlling said 25 generating means and/or said frequency shifting means in response thereto.

22. A communication system according to claim 21, wherein the characteristic relates to network capacity.

30

23. A communications system according to claim 21, wherein the characteristic relates to subscriber requirements.

- 26

24. A communications system according to any of claims 20 to 23, further comprising means for determining frequency spectrum availability in at least part of the communications system and means for controlling said frequency shifting means in response thereto.

25. A communication system according to any of claims 20 to 24, wherein at least one of the radio access network devices is arranged to communicate with a conventional mobile communication device.

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26. Apparatus for a communication system including transceiver equipment, said apparatus comprising means for outputting a signal suitable for transmission using a given communication protocol, said outputting means further being capable of outputting a signal suitable for transmission using a different communication protocol.

27. A method of operating a radio access network device, which comprises generating a signal for transmission in accordance with a given communication protocol, said generating means further being arranged to generate a signal for transmission in accordance with at least one further 20 communication protocol.

28. A method of operating a radio access device, which comprises converting a signal between a form suitable for transmission using a first communication protocol and at least a second communication protocol.

29. A method of operating a mobile communication device, which comprises generating a signal for transmission in accordance with a given communication protocol, said generating means further being arranged to generate a signal for transmission in accordance with at least one further 30 communication protocol.

30. A method of operating a mobile communication device, which

- 27 comprises converting a signal between a form suitable for transmission using a first communication protocol and at least a second communication protocol.

31. Apparatus for a communication system including transceiver 5 equipment, said apparatus comprising means for frequency shifting a signal in the frequency domain, said signal having been generated for transmission in accordance with a given communication protocol, and comprising means for selecting a frequency shift factor to be used for frequency shifting the signal.

10

32. Apparatus as claimed in claim 31, wherein the given communication protocol is a code division multiple access (COMA) communication protocol.

33. Apparatus for a communication system including transceiver equipment, said apparatus comprising means for frequency shifting a signal in 15 the frequency domain, said signal having been generated for transmission in accordance with a code division multiple access (COMA) communication protocol, and comprising means for selecting a frequency shift factor to be used for frequency shifting the signal.

20

34. Apparatus as claimed in any of the preceding claims, further comprising means for receiving a control signal and means for controlling said frequency shifting means in accordance with the control signal.

35. Apparatus as claimed in any of the preceding claims, wherein the 25 frequency shift factor selecting means is arranged to select the frequency shift factor on the basis of a network characteristic.

36. Apparatus as claimed in claim 35, wherein the characteristic relates to frequency spectrum availability.

37. Apparatus as claimed in any of the preceding claims, wherein the frequency shifting means is arranged for alternatively shifting the signal for

- 28 transmission in the frequency domain in accordance with a plurality of frequency shift factors.

38. Apparatus according to any of the preceding claims, further 5 comprising an amplifier for amplifying the signal before or after frequency conversion.

39. Apparatus according to claim 38, in which the amplifier is in the form of a linear amplifier.

40. Apparatus according to claim 38, in which the amplifier is in the form of a variable amplifier.

41. Apparatus according to any of claims 31 to 40, wherein the 15 frequency shifting means comprises a first frequency converter for converting uplink signals and a second frequency converter for converting downlink signals.

42. A mobile communication device comprising an antenna for 20 transmitting and/or receiving signals via a wireless communication medium; and apparatus according to any of the preceding claims for shifting the signal in the frequency domain.

43. A base station comprising an antenna for transmitting and/or 25 receiving signals via a wireless communication medium; and apparatus according to any of claims 31 to 41 for frequency converting the signals.

44. A communication system comprising one or more mobile communication devices according to claim 42 and one or more base stations 30 according to claim 43.

45. A method of converting apparatus configured to transmit and/or

- 29 receive signals in a first frequency band via a wireless communication medium, the method comprising installing apparatus according to any of claims 31 to 41 for shifting the signal in the frequency domain to at least one further frequency band.

46. A method of converting a code-division-multiplexed (CDMA) signal, the method comprising converting the COMA signal between a first frequency band and at least a second frequency band.

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47. A mobile communication device comprising an antenna for transmitting and/or receiving signals via a wireless communication medium; a frequency converter for converting the signals between a first frequency band and at least a second frequency band and means for selecting a frequency shift factor used for the frequency conversion,

48. The device of claim 47, wherein the frequency shift factor selecting means is arranged to select the frequency shift factor on the basis of a network characteristic. 20

49. The device of claim 48, wherein the characteristic relates to frequency spectrum availability.

50. The device of any of claims 47 to 49, further comprising means for receiving a control signal and means for controlling said frequency shifting 25 means in accordance with the control signal.

51. The device of any of claims 47 to 50 further comprising an amplifier for amplifying the signals before or after frequency conversion.

30

52. The device of claim 51, in which the amplifier is in the form of a linear amplifier.

- 30

53. The device of claim 51, in which the amplifier is in the form of a variable amplifier.

54. The device of any of claims 47 to 53 comprising a first frequency 5 converter for converting uplink signals; and a second frequency converter for converting downlink signals.

55. The device of any of claims 47 to 53 wherein the first or second frequency band includes a frequency between 400 and 500 MHz.

56. A communication system comprising one or more mobile communication devices according to any of claims 47 to 55; and one or more base stations, each base station comprising an antenna for transmitting and/or receiving signals via a wireless communication medium, and a frequency 15 converter for converting the signals between a first frequency band and at least a second frequency band and comprising means for selecting a frequency shift factor used for the frequency conversion.

57. A method of converting a mobile communication device configured to 20 transmit and/or receive signals in a first frequency band via a wireless communication medium, the method comprising installing a frequency converter into the device to convert the signals between the first frequency band and at least a second frequency band, said frequency converter comprising means for selecting a frequency shift factor used for the frequency 25 conversion.

58. A method of transmitting a signal from a mobile communication device, the method comprising generating a signal in a first frequency band, selecting a frequency factor to be used for converting the signal to at least a 30 second frequency band on the basis of a network characteristic, converting the signal into at least a second frequency band, and transmitting the converted signal from the mobile communication device.

- 31

59. A method of processing a signal at a mobile communication device, the method comprising receiving a signal in a first frequency band at the mobile communication device, and converting the signal at the mobile communication 5 device into at least a second frequency band.

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60. Apparatus for processing a code-division-multiplexed (CDMA) signal, the apparatus comprising a frequency converter for converting the CDMA signal between a first frequency band and at least a second frequency band.

61. Apparatus according to claim 60 further comprising an amplifier for amplifying the CDMA signal before or after frequency conversion.

62. Apparatus according to claim 60, in which the amplifier is in the form 15 of a linear amplifier.

63. Apparatus according to claim 60, in which the amplifier is in the form of a variable amplifier.

20

64. Apparatus according to any of claims 60 to 63 comprising a first frequency converter for converting uplink signals; and a second frequency converter for converting downlink signals.

65. Apparatus according to any of the preceding claims wherein the first 25 or second frequency band includes a frequency between 400 and 500 MHz.

66. A mobile communication device comprising an antenna for transmitting and/or receiving code-division-multiplexed (CDMA) signals via a wireless communication medium; and apparatus according to any of the 30 preceding claims for frequency converting the CDMA signals.

67. A base station comprising an antenna for transmitting and/or

- 32 receiving code-division-multiplexed (CDMA) signals via a wireless communication medium; and apparatus according to any of claims 60-64 for frequency converting the CDMA signals.

5

68. A communication system comprising one or more mobile communication devices according to claim 66 and one or more base stations according to claim 67.

69. A method of converting apparatus configured to transmit and/or 10 receive code-division-multiplexed (CDMA) signals in a first frequency band via a wireless communication medium, the method comprising installing apparatus according to any of claims 61 to 65 to convert the CDMA signals between the first frequency band and at least a second frequency band.

15

70. A method of converting a code-division-multiplexed (CDMA) signal, the method comprising converting the CDMA signal between a first frequency band and at least a second frequency band.

71. A mobile communication device comprising an antenna for 20 transmitting and/or receiving signals via a wireless communication medium; and a frequency converter for converting the signals between a first frequency band and at least a second frequency band.

72. The device of claim 71 further comprising an amplifier for amplifying 25 the signals before or after frequency conversion.

73. The device of claim 72, in which the amplifier is in the form of a linear amplifier. 30

74. The device of claim 72, in which the amplifier is in the form of a variable amplifier.

- 33

75. The device of any of claims 71 to 74 comprising a first frequency converter for converting uplink signals; and a second frequency converter for converting downlink signals.

5

76. The device of any of claims 71 to 75 wherein the first or second frequency band includes a frequency between 400 and 500 MHz

77. A communication system comprising one or more mobile communication devices according to any of claims 71 to 76; and one or more 10 base stations, each base station comprising an antenna for transmitting and/or receiving signals via a wireless communication medium, and a frequency converter for converting the signals between a first frequency band and at least a second frequency band.

15

78. A method of converting a mobile communication device configured to transmit and/or receive signals in a first frequency band via a wireless communication medium, the method comprising installing a frequency converter into the device to convert the signals between the first frequency band and at least a second frequency band.

79. A method of transmitting a signal from a mobile communication device, the method comprising generating a signal in a first frequency band, converting the signal into at least a second frequency band, and transmitting the converted signal from the mobile communication device.

80. A method of processing a signal at a mobile communication device, the method comprising receiving a signal in a first frequency band at the mobile communication device, and converting the signal at the mobile communication device into at least a second frequency band.

81. A converter/repeater substantially as described herein with reference to Figures 2 and 3 of the drawings.

- 34

82. A mobile communication device substantially as described herein with reference to Figure 2 of the drawings.

5

83. A base station substantially as described herein with reference to Figure 3 of the drawings.

84. A mobile communication system substantially as described herein with reference to Figures 1, 2 and 3 of the drawings

85. A method of processing a COMA signal substantially as described herein.

86. A method of converting apparatus substantially as described herein.

87. Apparatus substantially as herein described and illustrated with reference to Figures 4 and 5 of the drawings.

88. A mobile communications device substantially as herein described 20 and illustrated with reference to Figures 4 and 5 of the drawings.

89. A radio access network device substantially as herein described and illustrated with reference to Figures 4 and 5 of the drawings.

25

90. A communications system substantially as herein described and illustrated with reference to Figures 4 and 5 of the drawings.

91. A method of operating a mobile communication device substantially as herein described and illustrated with reference to Figures 4 and 5 of the 30 drawings.

92. A method of operating a radio network access device substantially

- 35 as herein described and illustrated with reference to Figures 4 and 5 of the drawings

93. An apparatus substantially as described herein with reference to 5 Figures 2 and 3 of the drawings.

94. A mobile communication device substantially as described herein with reference to Figure 2 of the drawings.

10

95. A base station substantially as described herein with reference to Figure 3 of the drawings.

96. A mobile communication system substantially as described herein with reference to Figures 1, 2 and 3 of the drawings.

97. A method of processing a signal substantially as described herein.

98. A method of converting apparatus substantially as described herein.