GB2358327A

GB2358327A - Control signalling in a mobile communications network

Info

Publication number: GB2358327A
Application number: GB0000762A
Authority: GB
Inventors: Behzad Mohebbi
Original assignee: Fujitsu Ltd
Current assignee: Fujitsu Ltd
Priority date: 2000-01-13
Filing date: 2000-01-13
Publication date: 2001-07-18
Also published as: GB0000762D0

Abstract

A mobile communications network includes a base station mobile stations. The base station comprises means for generating a sequence of pilot words, each pilot word of the sequence being made up of a predetermined first portion (Bit #0,1,3,4), and a second portion (Bit #2) that is varied in dependence upon an input signal to the pilot signal generator. The variable portion may be used to carry extra information (user data or control information such as transmission power control information) to the mobile stations using redundant bits of the pilot words.

Description

2358327 CONTROL SIGNALLING IN MOBILE COMMUNICATIONS NETWORKS The present

invention relates to control signalling in mobile communications networks, for example Wideband Code Division Multiple Access (W-CDMA) cellular networks.

Figure 1 of the accompanying drawings shows parts of a mobile communications network including a mobile station MS which is in two-way communication with a base station ES. The mobile station MS and base station BS have one or more uplink (or reverse link) channels for transmitting signals (user data and/or control signals) from the mobile station to the base station, and one or more downlink (or forward link) channels for transmitting signals (user data and/or control signals) from the base station to the mobile station. In some networks, the mobile station and base station have more than one uplink and/or downlink channel for two-way communication purposes. For example, there may be separate data and control channels in one or both directions.

The base station ES is also in two-way communication with a base station controller BSC of the network. The base station controller may also be referred to as a radio network controller (RNC).

Usually, several base stations are in communication with the same base station controller. The base station controller BSC is in turn in two-way communication with a mobile switching centre MSC. The base station controller BSC serves to manage the radio resources of its connected base stations, for example by performing hand-off and allocating radio channels.

The mobile switching centre MSC serves to provide switching functions and coordinates location registration and call delivery.

One W-CDMA mobile communications network currently under development by the European Telecommunications Standards Institute (ETSI) is referred to as a UTRA network. UTRA stands for UMTS Terrestrial Radio Access, and UMTS stands for Universal Mobile Telecommunication System (a third generation mobile telecommunications system). The proposed UTRA network is a Direct Sequence CDMA (DS-CDMA) network using frequency division duplexing (FDD). In such a FDD network, uplink and downlink channels are realised using different frequencies (spaced by 130MHz), and a physical channel is identified by a code and a frequency.

In W-CDMA there exist three types of dedicated physical channels, one for the downlink and two for the uplink, as illustrated in Figure 2 of the accompanying drawings. Within one downlink dedicated physical channel (DPCH) dedicated data generated at the data (for example the network link level (layer 2) and above layer, layer 3) is transmitted in time-multiplexed manner with control information generated at the physical layer (layer 1). The layer 1 control information consists of known pilot bits for downlink channel estimation, transmit power control commands (TPC) for uplink closed-loop power control, and an optional transport-format indicator (TFI) which describes the instantaneous parameters of the different transport channels multiplexed on the dedicated physical data channel (DPDCH), such as block size and number of blocks. Dedicated pilot bits are used instead of a common pilot in order to support, for example, the use of adaptive antenna arrays in the base station.

Dedicated pilot bits also allow for more efficient downlink closed-loop power control.

As shown in Figure 2, each radio frame has a length of 10ms and is split into 15 time slots each of length 0.667ms, corresponding to one power-control period. The number of bits per downlink time slot is not fixed but may vary in the range 20 to 1280, corresponding to a physical channel bit rate in the range 32 to 2048 kbits/s.

There are two types of dedicated physical channels defined for the W-CDMA uplink; the uplink dedicated physical data channel (uplink DPDCH) and the uplink dedicated physical control channel (uplink DPCCH). The DPDCH carries the layer 2 dedicated data, while the DPCCH carries the layer 1 control information. In the uplink direction, layer 2 data and layer 1 control information is transmitted in parallel on different physical channels I and Q using dual-channel Quaternary Phase Shift Keying (QPSK) for example. The uplink is layer 1 control information type is the same as for the downlink (i.e. pilot bits, power-control commands for downlink closed-loop power control, and a TFI). There may also be a Feedback Information (FBI) field. On the uplink, the number of bits per time slot may vary in the range 10 to 640, corresponding to a physical channel bit rate in the range 16 to 1024 kbits/s.

As mentioned above, in presently-proposed third generation systems, both forward and reverse links enjoy closed-loop transmit power control commands which are issued by the TPC field in the DPCCH 15 times every

10ms. There are two symbols (four bits) allocated for each TPC command, providing adequate performance for most operational scenarios. The power control commands (TPC bits) constitute a channel bit rate of about 3.2 kbits/s, which is a considerable system overhead.

Further, more system overhead is required if the performance of the power-control mechanism is to be improved, say in the soft hand-off region, where a number of links may suffer excess path loss, leading to high bit error rate (BER) on the received TPCs. The high BER on the non-optimum forward and reverse links in soft hand-off usually causes transmission power errors, which either lead to reduced capacity or high frame error rate (FER). In addition, in DS-CDMA cellular systems, all signal sequences arriving at the receiver must be power-controlled to an accuracy of around 1 dB to prevent strong signals from suppressing the weak ones. This effect is referred to as the "near-far problem" and is more pronounced the more removed the receiver is from an optimal structure. The near-far problem necessitates the use of adaptive fast power control. DS-CDMA cellular systems suffer from this near-far problem and require accurate fast power control mechanisms to ensure that no single user transmits more power than required for adequate detection, which would cause degradation on other users received signal.

It is therefore desirable to provide additional TPC bits in each frame or each time slot, so as to improve the speed and/or accuracy of power control. It is also desirable to be able to transmit more control and/or user information in each frame or time slot.

According to a first aspect of the present invention there is provided a mobile communications network including first and second stations, one of said first and second stations being a base station of the network and the other station being a mobile station of the network, wherein: said first station comprises: pilot word sequence generation means, having an input for receiving an input signal, and operable to generate a sequence of pilot words, each pilot word of said sequence being made up of a predetermined first portion, independent of said input signal, and a second portion that is varied in dependence upon said input signal; and transmission means for transmitting the generated sequence of pilot words to said second station; and said second station comprises: receiving means for receiving such a sequence of pilot words transmitted from said first station; and pilot word sequence decoding means operable to receive the said sequence of pilot words received by the receiving means and to derive from the said second portion of such a pilot word of the received sequence an output signal corresponding to the said input signal.

According to a second aspect of the present invention there is provided a base station, for use in a mobile communications network, comprising: pilot word sequence generation means, having an input for receiving an input signal, and operable to generate a sequence of pilot words, each pilot word of said sequence being made up of a predetermined first is portion, independent of said input signal, and a second portion that is varied in dependence upon said input signal; and transmission means for transmitting the generated sequence of pilot words to a mobile station of the network.

According to a third aspect of the present invention there is provided a base station, for use in a mobile communications network, comprising: receiving means for receiving from a mobile station of the network a sequence of pilot words, each pilot word of said sequence being made up of a predetermined first portion, independent of a transfer signal to be sent from the mobile station to the base station, and a second portion that is varied by the mobile station in dependence upon said transfer signal; and pilot word sequence decoding means operable to receive the said sequence of pilot words received by the receiving means and to derive from the said second portion of such a pilot word of the received sequence an output signal corresponding to the said transfer signal.

According to a fourth aspect of the present invention there is provided a mobile station, for use in a mobile communications network, comprising: pilot word sequence generation means, having an input for receiving an input signal, and operable to generate a sequence of pilot words, each pilot word of said sequence being made up of a predetermined first portion, independent of said input signal, and a second portion that is varied in dependence upon said input signal; and transmission means for transmitting the generated sequence of pilot words to a base station of the network.

According to a fifth aspect of the present invention there is provided a mobile station, for use in a mobile communications network, comprising:

receiving means for receiving from a base station of is the network a sequence of pilot words, each pilot word of said sequence being made up of a predetermined first portion, independent of a transfer signal to be sent from the base station to the mobile station, and a second portion that is varied by the base station in dependence upon said transfer signal; and pilot word sequence decoding means operable to receive the said sequence of pilot words received by the receiving means:' and to derive from the said second portion of such a pilot word of the received sequence an output signal corresponding to the said transfer signal.

According to a sixth aspect of the present invention there is provided a signalling method, for use in a mobile communications network that includes first and second stations, one of said first and second stations being a base station of the network and the other station being a mobile station of the network, the method comprising the steps of: in said first station: receiving an input signal; generating a sequence of pilot words, each pilot word of said sequence being made up of a predetermined first portion, independent of said input signal, and a second portion that is varied in dependence upon said input signal; and transmitting the generated sequence of pilot words to said second station; and in said second station: receiving such a sequence of pilot words transmitted from said first station; and deriving from the said second portion of such a pilot word of the received sequence an output signal corresponding to the said input signal.

With such aspects of the invention it is possible to provide additional TPC bits in each frame or each time slot so as to improve the speed and/or accuracy of power control. It is also possible to be able to transmit more control and/or user information in each frame or time slot.

is Reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1, discussed hereinbefore, shows a schematic view of parts of a mobile communications network; Figure 2, discussed hereinbefore, illustrates one example of a frame structure of uplink and downlink dedicated physical channels; Figure 3 shows an example of a series of uplink pilot bit patterns where the number of pilot bits is 5; Figure 4 shows an example of a series of uplink pilot bit patterns where the number of pilot bits is 6; Figure 5 shows an example of a series of uplink pilot bit patterns where the number of pilot bits is 7; Figure 6 shows an example of a series of uplink pilot bit patterns where the number of pilot bits is 8; Figure 7 shows an example of a series of downlink pilot bit patterns where the number of pilot bits is 4; Figure 8 shows an example of a series of downlink pilot bit patterns where the number of pilot bits is 8; Figure 9 shows an example of a series of downlink pilot bit patterns where the number of pilot bits is 16; Figure 10 shows an example of a series of downlink pilot bit patterns for diversity antennas where the number of pilot bits is 4; Figure 11 shows an example of a series of downlink pilot bit patterns for diversity antennas where the number of pilot bits is 8; Figure 12 shows an example of a series of downlink pilot bit patterns for diversity antennas where the number of pilot bits is 16; Figure 13 is a block diagram showing parts of a mobile station and a base station erforming two-wa p y communication over a dedicated physical channel; Figure 14 is a block diagram showing parts-of the dedicated physical channel generator of Figure 13; Figure 15 is a block diagram showing parts of the dedicated physical channel extractor of the base station of Figure 13; Figure 16 is a block diagram showing parts of the dedicated physical channel generator of the base station of figure 13; Figure 17 is a block diagram showing parts of the dedicated physical channel extractor of the mobile station of Figure 13; t Figure 18 shows an example of a sequence of pilo code-words in an embodiment of the present invention; Figure 19 shows an example of an extended pilot code-word family for use in an embodiment of the present invention; Figure 20 is a block diagram showing parts of a mobile station and a base station embodying the present invention; Figure 21 is a block diagram showing parts of the dedicated physical channel generator of the mobile station of Figure 20; Figure 22 is a block diagram showing parts of the dedicated physical channel extractor of the base station of Figure 20; Figure 23 is a block diagram showing parts of the dedicated physical channel generator of the base station of Figure 20; Figure 24 is a block diagram showing parts of the dedicated physical channel extractor of the mobile station of Figure 20; and Figure 25 is a block diagram showing another example of a dedicated channel generator embodying the present invention.

As mentioned above, in the proposed UTRA W-CMA cellular network, dedicated pilot bits are transmitted on the DPCCH of both the forward and reverse links in is each time slot. The number of pilot bits per time slot has been specified to range from 2 to 16 for the forward link and 3 to 8 for the reverse link. The pilot bits in each time slot are code-word modulated so that the time slot and frame identity can readily be obtained.

Figure 3 shows an example of a series of pilot bit patterns for transmission in the 15 different time slots of a frame of an uplink dedicated physical control channel (DPCCH) for the case where the number of pilot bits per time slot is equal to 5. Each pilot bit pattern in a time slot can be referred to as a "pilot code-word". As mentioned above, since the sequence of pilot code-words is known, it can be used both for channel estimation purposes and for frame synchronisation purposes.

In general only certain bits of the pilot code words actually change from one time slot to the next, the remaining bits staying fixed at, for example, the level '1111. As such therefore, these fixed bits are not useable for time slot identification or frame synchronisation purposes, but can optionally be used for channel estimation. For example, as shown in Figure 3 (for the case where the number of pilot bits for the uplink DPCCH is 5) four bits (#0, #1, #3, and #4) are varied from one time slot to the next in a predetermined sequence but one of the bits (# 2 indicated by an arrow) is fixed at the level I'll, for all time slots.

An example of a case where the number of pilot bits is 6 is shown in Figure 4. In this case, two of the pilot bits (#0 and #3 indicated by arrows) do not carry any varying information, and are set at the level.

11111.

Figures 5 and 6 show similar examples for the cases where the number of pilot bits is 7 and 8 respectively. In both cases, only four bits are varying, the rest being set in all time slots to the level 1.

For the downlink dedicated physical channel, two pilot bits are transmitted in parallel, one on the I branch and one on the Q-branch. Each such two-bit transmission is referred to as a "symbol". Figure 7 shows one example of a series of pilot symbol patterns for the downlink dedicated physical control channel.

In Figure 7, one of the pilot symbols (#0 indicated by an arrow) is non-varying and its two bits are both set to the value 1. Figures 8 and 9 show the cases where the numbers of pilot bits are 8 and 16 respectively (corresponding to 4 and 8 pilot symbols respectively).

Finally, Figures 10 to 12 show examples of pilot bit patterns of the dedicated physical channel when diversity antennas are used, making use of Space Time Transmit Diversity (STTD).

Figure 13 is a block diagram showing parts of a mobile station 100 and a base station 200 in two-way communication using a dedicated physical channel DPCH in each direction. The mobile station 100 includes dedicated physical channel (DPCH) generator 110 and a dedicated physical channel (DPCH) extractor 120. The base station 200 includes a dedicated physical channel extractor (DPCH) 220 and a dedicated physical channel (DPCH) generator 210.

The DPCH generator 110 of the mobile station 100 serves to generate uplink DPDCH and DPCCH signals (together, uplink DPCH signals), as described above with reference to Figure 2, for transmission in the uplink direction to the base station 200. In the base station the uplink DPCH signals are received and extracted by the DPCH extractor 210.

The DPCH generator 210 of the base station 200 serves to generate the downlink DPCCH and DPDCH signals is (together, downlink DPCH signals), which are time multiplexed into each time slot, as described above with reference to Figure 2, and transmitted on the downlink to the mobile station 100. In the mobile station the downlink DPCH signals are received and extracted by the DPCH extractor 120.

Figure 14 is a block diagram showing parts of the DPCH generator 110 of the mobile station 100. The MS DPCH generator 110 includes a data generator 112, an optional TFI generator 114, a TPC generator 116, a pilot generator 118, and a time division multiplexer 119.

User data for transmission to the base station 200 are generated by the data generator 112 and are transmitted on the dedicated physical data channel (DPDCH) over the I-branch. The outputs of the TFI generator 114, the TPC generator 116, and the pilot generator 118 are time division multiplexed by the multiplexer 119 and transmitted on the dedicated physical control channel (DPCCH) in the format shown in Figure 2, and transmitted on the Q-branch. As mentioned above, the transport format indicator (TFI) -12 1 field of the DPCCH is optional. The uplink pilot generator 118 contains, for example, a look-up table having entries corresponding respectively for the different time slots of a frame and generates over the course of a frame a predetermined sequence of pilot j words as described above with reference to Figures 3 to 6.

Figure 15 is a block diagram showing parts of the dedicated physical channel (DPCH) extractor 220 of the base station 200. The BS DPCH extractor 220 contains a data extractor 222, an optional TFI extractor 224, a TPC extractor 226, a pilot extractor 228 and a time division demultiplexer 229.

DPDCH signals received by the base station 200 via is the I-branch are passed to the data extractor 222 where the user data transmitted from the mobile station 100 is extracted.

DPCCH signals which are received by the base station 200 via the Q-branch are first time division demultiplexed by the demultiplexer 229 to separate the portions belonging to the TFI, TPC, and pilot fields of the DPCCH, and these portions are passed to the TFI extractor 224, the TPC extractor 226, and the pilot extractor 228 respectively.

The pilot bits transmitted on the DPCCH from the mobile station 100 are extracted by the pilot extractor 228 and are then used for channel estimation purpose! and/or for frame synchronisation or time slot identification purposes, as mentioned above.

Figure 16 is a block diagram showing parts of the DPCH generator 210 of the base station 200 shown in Figure 13. The BS DPCH generator 210 is generally similar to the MS DPCH generator 110 described above.

and comprises a data generator 212, an optional TFI generator 214, a TPC generator 216, a pilot generator 217, and first and second time division multiplexers 218 and 219.

The data generator 212 of the base station 200 performs a similar function to the data generator 112 of the mobile station 100. The TFI generator 214 of the base station 200 performs a similar function to the TFI generator 114 of the mobile station 100. The TPC generator 216 of the base station 200 performs a similar function to the TPC generator 11G of the mobile station 100. The pilot generator 217 of the base station 200 performs a similar function to the pilot generator 118 of the mobile station 100.

In the DPCH generator 210 of the base station 200, the outputs of the TFI generator 214, the TPC generator 216 and the pilot generator 217 are time division multiplexed by the first multiplexer 218 to form a dedicated physical control channel (DPCCH) signal which is then itself time-division multiplexed by the second multiplexer 219 with the dedicated physical data channel (DPDCH) signal output from the data generator 212 to form a dedicated physical channel (DPCH) signal for transmission to the mobile station 100 using both I and Q branches.

Figure 17 shows parts of the DPCH extractor 120 of the mobile station 100. The MS DPCH extractor 120 of the mobile station 100 is generally similar to the ES DPCH extractor 220 of the base station 200, and comprises a data extractor 122, an optional TFI extractor 124, a TPC extractor 126, a pilot extractor 127, and first and second time division demultiplexers 128 and 129.

The data extractor 122 of the mobile station 100 performs a similar function to the data extractor 222 of the base station 200. The TFI extractor 124 of the mobile station 100 performs a similar function to the TFI extractor 224 of the base station 200. The TPC extractor 126 of the mobile station 100 performs a similar function to the TPC extractor 226 of the base station 200. The pilot extractor 127 of the mobile station 100 performs a similar function to the pilot extractor 228 of the base station 200.

DPCH signals received on the downlink from the base station 200 are time demultiplexed by the second demultiplexer 129 into the constituent dedicated physical data (DPDCH) channel and dedicated physical control channel (DPCCH) signal portions. The DPDCH signal portion is then passed to the data extractor 122, where the user data is extracted. The DPCCH signal portion is further split by the first demultiplexer 128 into portions corresponding respectively to the TFI, TPC and pilot fields which are passed to the TFI extractor 124, the TPC extractor 126 and the pilot extractor 127 respectively.

The MS pilot extractor 127 extracts the pilot bits transmitted from the base station 200, which are subsequently used for channel estimation and/or frame synchronisation etc.

1 As described above, it is presently proposed that one or more bits within the known sequence of pilot words transmitted on the DPCCH will remain at a constant value, for example the value 1, in all the i time slots. In embodiments of the present invention, it is proposed to use these bits ("redundant" bits), which are not essential for distinguishing between time slots, for other purposes. For example, they may be used to carry additional TPC and possibly other system information on both the forward and reverse links.

The redundant bit(s) may be changed from one time slot to the next, allowing one or more extra bits of information to be transmitted per time slot using the redundant bit(s), as shown in Figure 18.

Another possibility is that each redundant pilot bit is set to the same value over a plurality of time -is- slots within a single frame, or even throughout the whole frame. In this way only information which varies at less than the time slot rate (e.g. at the frame rate may be conveyed by using the redundant bits, but error checking and possibly channel estimation using the redundant bits can be carried out as the redundant bits will be predictable.

Because the redundant bit(s) can be 1 or 0, effectively an extended pilot code-word family now exists, made up of two or more different code-word sequences. In the above-described case where the uplink pilot code-word comprises 5 bits, with just one redundant bit as illustrated in Figure 3, signalling can be accomplished by selecting between two separate is code-word sequences, one in which the redundant bit of each code word is set to the value 1, and the other where the redundant bit of each code word is set at the level 0. Figure 19 shows the two sequences A and B. By switching between the use of sequence A and sequence B, information can be conveyed by using the previously redundant pilot bit. Generally, where 11p11 redundant bits are used for signalling purposes, the number of code-word sequences is 21.

Incidentally, in the currently-proposed third generation systems, although the redundant pilot bits are non-varying and are therefore not useful for frame synchronisation purposes, they can still be used for channel estimation. When these bits are used to convey other data in every time slot, they can no longer be used for channel estimation since they no longer have an expected (predictable) value on the receiving side.

Predictability can be restored, to some extent, by repeating the same value in, say, two or more consecutive time slots but even in this case some efficiency in channel estimation will be lost. There is therefore a trade-off to be considered between an increase in data throughput and the desired accuracy/efficiency of channel estimation. However, iall many instances it is desirable to trade off accuracy/efficiency of channel estimation (which may already be desirably high) for improvements in signalling such as faster and more accurate power control, for example.

Figure 20 is a block diagram showing parts of a mobile station 300 and a base station 400 embodying the 11 present invention in two-way communication over a dedicated physical channel. The mobile station 300 includes a dedicated physical channel (DPCH) generator 310 and a dedicated physical channel (DPCH) extractor 320. The base station 400 includes a dedicated physical channel extractor (DPCH) 420 and a dedicated physical channel (DPCH) generator 410. These parts are generally similar to corresponding parts of the above described Figure 13 example, but contain additional features which are described below.

Figure 21 is a block diagram showing parts of the DPCH generator 310 of the mobile station 300 embodying the present invention. The MS DPCH generator 310 includes a data generator 112, an optional TFI generator 114, a TPC generator 116 and a time multiplexer 119. These parts are the same as the corresponding parts of Figure 14 that bear the same reference numerals. In place of the pilot generator 118 of Figure 14 is a pilot generator 318, an extended pilot generator 350 and a multiplexer 360.

User data for transmission to the base station 4 0 are generated by the data generator 112 and transmitted:

on the dedicated physical data channel (DPDCH) over the I-branch.

The uplink pilot generator 318 is used for generating the predetermined portion of each pilot word, i.e. those bits of the known sequence of pilotwords which change from one time slot to the next in a predetermined manner (those bits illustrated in Figures 3 to 6 which are not highlighted by an arrow). For this purpose, the pilot generator may contain, for example, a look-up table in which at least the respective predetermined portions of the pilot words of the known sequence are stored.

The uplink extended pilot generator 350 is used for generating the remaining portion of each pilot word, i.e. the previously redundant bits indicated by the arrows in Figures 3 to 6. In this embodiment, the pilot generator 318 informs the extended pilot generator 350 of the number of bits in the remaining portion purposes by sending it a signal NUM.

The extended pilot generator 350 also receives an input signal EXT which contains data to be transmitted over the redundant pilot bits. This data may be derived from many possible sources. In one embodiment the EXT data may be provided by the TPC generator 116 so that extra power control signalling may be conveyed.

In another embodiment the EXT data may be provided by the data generator 112 so that extra user data can be transmitted over the control channel to increase data throughput. Alternatively EXT data may be provided by a combination of such sources so that more than one type of extra data is carried by the previously-redundant bits.

The predetermined portion of the pilot word output by the pilot generator 318 and the remaining portion of the pilot word output by the extended pilot generator 350 are then combined (interleaved) by the multiplexer 360 to form the complete pilot code-word.

The outputs of the TFI generator 114, the TPC generator 116, and the multiplexer 360 are time division multiplexed by the multiplexer 119 and transmitted on the Q-branch of the dedicated physical control channel (DPCCH) in the format as shown in Figure 2.

Figure 22 is a block diagram showing parts of the dedicated physical channel (DPCH) extractor 420 of the base station 400 embodying the present invention. The BS DPCH extractor 420 contains a data extractor 222, an optional TFI extractor 224, a TPC extractor 226 and a time demultiplexer 229. These parts are the same as the corresponding parts of Figure 15 that bear the same reference numerals. In place of the pilot extractor 228 of Figure 15 is a pilot extractor 428, an extended pilot extractor 450 and a demultiplexer 460.

DPDCH signals received by the base station 400 via the I branch are passed to the data extractor 222 where the user data transmitted from the mobile station 300 is are extracted.

DPCCH signals which are received by the base station 400 are first time demultiplexed by the j demultiplexer 229 to separate the TFI, TPC, and pilot fields from the DPCCH, and these fields are passed to the TFI extractor 224, the TPC extractor 226, and the demultiplexer 460 respectively.

The demultiplexer 460 separates those bits of each pilot word which belong to the predetermined portion (i.e. those bits illustrated in Figures 3 to 6 which are not highlighted by an arrow) from the bits belonging to the remaining portion (i.e. the previously-redundant bits indicated by the arrows in Figures 3 to 6). These two sets of bits are then passed to the pilot extractor 428 and extended pilot extractor 450 respectively where they are extracted and processed. The extended pilot extractor 450 produces an output signal EXT which corresponds to the input signal EXT of the extended pilot generator 350 of Figure 20.

Figure 23 is a block diagram showing parts of the DPCH generator 410 of the base station 400 embodying the present invention. The BS DPCH generator 410 is generally similar to the MS DPCH generator 310 described above with reference to Figure 20, and comprises a data generator 212, an optional TFI generator 214, a TPC generator 216, a pilot generator 417, an extended pilot generator 470, a first multiplexer 480, a second multiplexer 218, and a third multiplexer 219.

The data generator 212 of the base station 400 performs a similar function to the data generator 112 of the mobile station 300. The TFI generator 214 of the base station 400 performs a similar function to the TFI generator 114 of the mobile station 300. The TPC generator 216 of the base station 400 performs a is similar function to the TPC generator 116 of the mobile station 300. The pilot generator 417 of the base station 400 performs a similar function to the pilot generator 318 of the mobile station 300. The extended pilot generator 470 of the base station 400 performs a similar function to the extended pilot generator 350 of the mobile station 300 and also receives similar NUM and EXT signals as described above.

In this case, extra information to be sent from the base station 400 to the mobile station 300 is supplied to the extended pilot generator 350 in the input signal EXT. In each time slot the predetermined portion of each pilot word (i.e. the bits not marked by an arrow in Figs. 7 to 12) are provided by the pilot generator 417, and the remaining portion of each pilot word (i.e. the bits in Figures 7 to 12 indicated by arrows) is provided by the extended pilot generator 470 based on the applied input signal EXT. The predetermined and remaining portions are then combined (interleaved) as appropriate by the first multiplexer 480 to produce the complete pilot word for the time slot concerned.

In the DPCH generator 410 of the base station 400, respective output signals of the TFI generator 214, the TPC generator 216 and the first multiplexer 480 are time-division multiplexed by the second multiplexer 218 to form a dedicated physical control channel (DPCCH) signal which is then itself time division multiplexed by the third multiplexer 219 with a dedicated physical data channel (DPDCH) signal output from the data generator 212 to form a dedicated physical channel (DPCH) signal for transmission to the mobile station 300 using both the I and Q branches.

Figure 24 shows parts of the DPCH extractor 320 of the mobile station 300. The MS DPCH extractor 320 of the mobile station 300 is generally similar to the ES DPCH extractor 420 of the base station 400 illustrated in Figure 21, and comprises a data extractor 122, an optional TFI extractor 124, a TPC extractor 126, a pilot extractor 327, an extended pilot extractor 370, a first demultiplexer 380, a second demultiplexer 128 and a third demultiplexer 129.

I The data extractor 122 of the mobile station 300 performs a similar function to the data extractor 222 I of the base station 400. The TFI extractor 124 of the mobile station 300 performs a similar function to the TFI extractor 224 of the base station 400. The TPC extractor 126 of the mobile station 300 performs a similar function to the TPC extractor 226 of the base station 400. The pilot extractor 327 of the mobile station 300 performs a similar function to the pilot extractor 428 of the base station 400. The extended pilot extractor 370 of the mobile station 300 performs a similar function to the extended pilot extractor 450 of the base station 400. An output signal EXT is output from the extended pilot extractor 370 which corresponds to the input signal EXT to the extended pilot generator 470 of Figure 22.

It will be appreciated that generation of the sequence of pilot code words can be effected in various ways, and is not restricted to the method as described above. For example, Figure 25 shows an alternative embodiment of a mobile station DPCH generator to that described above with reference to Figure 21. The DPCH generator 510 in Figure 24 contains a pilot generator 575 which contains two pilot code-word look-up tables 585A and 585B Each look-up table stores a sequence of pilot code-words, and not only is the predetermined portion of each word stored but so is one possible value (or combination of values) of the bit (or bits) of the remaining (input-signal-dependent) portion. Each such look-up table stores a different combination of the remaining-portion bits. For example, in the case as described above with reference to Figure 3, where the number of pilot bits is 5 and the number of redundant pilot bits is 1, there are two pilot code-word look-up tables 585A and 585B corresponding respectively to the two possible values of the remaining-portion bit: a remaining-portion bit value of zero and a remaining portion bit value of 1. There are therefore two possible sequences A and B, as illustrated above with 2S reference to Figure 19. The look-up table 585A therefore stores the pilot words of sequence A in Figure 19 and the look-up table 585B stores the pilot words of sequence B in Figure 19.

In the Figure 25 embodiment, the EXT input to the pilot generator 575 controls which look-up table is accessed in each time slot. The accessed code-word is output from the pilot generator 575 and processed by the time division multiplexer 119 to form the DPCCH signal. The input signal EXT may vary from one time slot to another.

The signalling methods described above may be used to carry auxiliary TPC bits to compliment the existing TPC bits, such that the overall TPC BER can be reduced. or it could replace the TPC field such that the TPC

11 performance is similar or improved with reduced signalling overheads. It could also be used to carry 1 1 j feedback information (FBI) for antenna and/or cell selection (including the puncturing technique) or for i back-haul reduction, or for any other signalling purposes.

j

Claims

CLAIMS:

1. A mobile communications network including first and second stations, one of said first and second stations being a base station of the network and the other station being a mobile station of the network, wherein:

said first station comprises:

pilot word sequence generation means, having an input for receiving an input signal, and operable to generate a sequence of pilot words, each pilot word of said sequence being made up of a predetermined first portion, independent of said input signal, and a second portion that is varied in dependence upon said input signal; and transmission means for transmitting the generated sequence of pilot words to said second station; and said second station comprises:

receiving means for receiving such a sequence of pilot words transmitted from said first station; and pilot word sequence decoding means operable to receive the said sequence of pilot words received by the receiving means and to derive from the said second portion of such a pilot word of the received sequence an output signal corresponding to the said input signal.

2. A mobile communications network as claimed in claim 1, wherein said second station further comprises channel estimation means operable to employ the first portions of the received pilot words to produce channel estimation information relating to a communications channel used for transmitting the said sequence from the first station to the second station.

3. A mobile communications network as claimed claim 1 or 2, wherein said first station further comprises power control means operable to produce power control information for controlling the power of transmissions from the second station to the first station, and wherein such power control information is included in said input signal such that said second portions are varied in dependence upon such power control information.

4. A mobile communications network as claimed in any preceding claim, wherein said first station further comprises data generation means operable to produce user data for transmission to said second station, and wherein such user data is included in said input signal such that said second portions are varied in dependence upon such user data.

5. A mobile communications network as claimed in any:1 is preceding claim, wherein said input signal includes control information generated by the first station for use by the network.

6. A mobile communications network as claimed in any preceding claim, wherein the communications network is a wideband code division multiple access network.

7. A mobile communications network as claimed in any preceding claim, wherein the first station transmits a series of transmission frames to the second station, each frame being made up of a predetermined number of time slots, and one such pilot word of the said sequence is transmitted in each said time slot.

8. A mobile communications network as claimed in claim 7, wherein the pilot words transmitted in two or more time slots of the same frame have different respective said second portions.

9. A mobile communications network as claimed in claim 7, wherein the pilot words transmitted in all time slots of the same frame have the same respective second portions.

10. A base station, for use in a mobile communications network, comprising:

pilot word sequence generation means, having an input for receiving an input signal, and operable to generate a sequence of pilot words, each pilot word of said sequence being made up of.a predetermined first portion, independent of said input signal, and a second portion that is varied in dependence upon said input signal; and transmission means for transmitting the generated sequence of pilot words to a mobile station of the network.

11. A base station, for use in a mobile communications network, comprising:

receiving means for receiving from a mobile station of the network a sequence of pilot words, each is pilot word of said sequence being made up of a predetermined first portion, independent of a transfer signal to be sent from the mobile station to the base station, and a second portion that is varied by the mobile station in dependence upon said transfer signal; and pilot word sequence decoding means operable to receive the said sequence of pilot words received by the receiving means and to derive from the said second portion of such a pilot word of the received sequence an output signal corresponding to the said transfer signal.

12. A mobile station, for use in a mobile communications network, comprising:

pilot word sequence generation means, having an input for receiving an input signal, and operable to generate a sequence of pilot words, each pilot word of said sequence being made up of a predetermined first portion, independent of said input signal, and a second portion that is varied in dependence upon said input signal; and transmission means for transmitting the generated 1, sequence of pilot words to a base station of the network.

13. A mobile station, for use in a mobile communications network, comprising:

receiving means for receiving from a base station of the network a sequence of pilot words, each pilot word of said sequence being made up of a predetermined first portion, independent of a transfer signal to be sent from the base station to the mobile station, and a 11 second portion that is varied by the base station in dependence upon said transfer signal; and pilot word sequence decoding means operable to receive the said sequence of pilot words received by the receiving means and to derive from the said second is portion of such a pilot word of the received sequence an output signal corresponding to the said transfer signal.

14. A signalling method, for use in a mobile communications network that includes first and second!1 stations, one of said first and second stations being a base station of the network and the other station being a mobile station of the network, the method comprising the steps of:

in said first station:

receiving an input signal; generating a sequence of pilot words, each pilot word of said sequence being made up of a predetermined first portion, independent of said input signal, and a second portion that is varied in dependence upon said input signal; and transmitting the generated sequence of pilot words to said second station; and in said second station:

receiving such a sequence of pilot words transmitted from said first station; and deriving from the said second portion of such a pilot word of the received sequence an output signal corresponding to the said input signal.

15. A mobile communications network substantially as hereinbefore described with reference to and as illustrated in Figures 18 to 25.

16. A mobile station substantially as hereinbefore described with reference to and as illustrated in Figures 18 to 25.

17. A base station substantially as hereinbefore described with reference to and as illustrated in Figures 18 to 25.

18. A signalling method, for use in a mobile communications network, substantially as hereinbefore described with reference to and as illustrated in is Figures 18 to 25.