CN100557988C - Reduce the wireless communication system of frequency repeat utilization ratio - Google Patents

Abstract

The present invention relates to a kind of receiver and communication system that reduces frequency repeat utilization ratio.Described receiver is a kind of simple interference suppressing receiver or many decoding units interference suppressing receiver, comprise that signal processing unit suppresses and offset unit with disturbing, described signal processing unit is used for each the road signal that receives is carried out demodulation, separates mapping and channel-decoding processing; Described interference inhibition and offset unit are used for each the road interference between signals that receives is suppressed and offsets processing.Base station in the described communication system or subscriber station comprise described simple interference suppressing receiver or many decoding units interference suppressing receiver.Realization of the present invention can effectively overcome existing kind of co-channel interference, effectively shortens multiplex distance, reduces frequency repeat utilization ratio, increases honeycomb system capacity.Even all sub-districts of cellular system can only use with a kind of frequency, need not the complicated network planning and power control techniques.

Description

Wireless communication system for reducing frequency reuse rate

Technical Field

The present invention relates to the field of wireless communication technologies, and in particular, to a wireless communication system for reducing frequency reuse rate.

Background

It has been theoretically demonstrated that the use of multiple transmit antennas can divide a wireless channel into multiple parallel narrowband channels, with the potential to increase the bit transmission rate of the channel, and research results show that the channel capacity increases linearly with the number of antennas. Compared with receive diversity and smart antennas, MIMO (multiple input multiple output) systems can not only provide diversity gain and array gain, but also increase system capacity in SDM (spatial multiplexing).

BLAST is a way to improve bandwidth availability in wireless communications using spatial multiplexing techniques, and is called bell labs layered space-time architecture. The BLAST system simultaneously transmits parallel data streams in the same frequency band using a plurality of antennas, propagates different data streams using rich multi-paths, and can perform separation at a receiver, thereby obtaining spatial diversity.

The principle of BLAST is shown in FIG. 1. The same modulation scheme is used for a plurality of transmitters, and the same demodulation scheme is used for a plurality of receivers. BLAST divides a data stream of a single user into a plurality of sub-streams, and simultaneously transmits the parallel sub-streams using a plurality of antennas, and all sub-streams are transmitted in the same frequency band, so that spectrum use efficiency is high. There are multiple copies of the desired data into the channel (transmit antennas) and multiple outputs (receive antennas). At the receiver end, multiple antennas sort out multiple transmitted data sub-streams and their scattered copies, each receiving antenna receives all the transmitted data sub-streams superimposed together, and the data sub-streams can be separated and detected by the difference of these sub-channels using complex signal processing techniques.

Since the number of antennas of either the transmitter or the receiver is limited, increasing the diversity gain and increasing the transmission rate are a pair of contradictions. STC (space time code) and SFC (space frequency code) can solve this contradiction well. Space-time codes take advantage of the spatial diversity provided by multi-antenna systems, the performance of which depends on the number of antennas in the system and the coding of the signal in space and time, including space-time block codes and space-time trellis codes. These codes are designed assuming non-multipath channel conditions, belonging to narrowband codes, with the maximum achievable diversity gain equal to the product of the number of transmit antennas and the number of receive antennas.

The performance of space-time codes is not optimal under wideband multipath channel conditions because it exploits only spatial diversity and fails to exploit the channel frequency diversity provided by multipath. Therefore, in the research of the coding problem of a multi-antenna system based on OFDM (orthogonal frequency division multiplexing) in a multipath environment, the concept of space-frequency codes is proposed, and the diversity gain which can be potentially realized by the codes is the product of the number of transmitting antennas, the number of receiving antennas and the channel impulse response length (the number of multipath channels).

From the view of coherence time and coherence bandwidth of fading channel, space-time code requires that the channel fading time response remains approximately constant within one code block period spanning several OFDM characters, i.e. the larger the coherence time, the better; whereas space-frequency codes require that the channel fading frequency response of a code block across several subcarriers remains approximately constant, i.e. the larger the coherence bandwidth the better. From the constraint point of view, space-time codes have better performance in flat fading channels, while space-frequency codes have better performance in fast fading channels. However, in practice, the transmitter cannot predict the channel state information, and for this reason, the advantage of space-time codes and space-frequency codes can be combined, an STFC (space-time-frequency code) scheme is proposed, which is considered jointly in the space domain, the time domain and the frequency domain, thereby achieving the maximum diversity gain under the multi-antenna fading channel.

Based on the space-time/space-frequency/space-time-frequency/space-multiplexing coding processing technology, the structures of the transmitter and the receiver applied in the wireless communication system in the prior art are shown in fig. 6 to fig. 15, and different frequencies are required to be adopted for transmitting the transmitter which needs to transmit signals to the same receiver, so as to avoid co-frequency interference.

In cellular systems, since frequency resources are limited, frequency reuse is an effective means to improve frequency utilization. In a cellular system based on frequency reuse, adjacent co-frequency BSs (base stations) are covered by a family of cells using different frequencies, and the number of frequency reuse family cells (i.e., the cells using different frequencies) is represented by N. Assuming that the system has K frequency points, in the frequency reuse family, each cell is divided into J frequency points (J < K), then there are

K-JN-constant.

If the frequency reuse family is repeated M times in a certain region, the system capacity C of the region is:

C＝MK。

system capacity C is proportional to M, which is inversely proportional to N. The cellular system capacity is maximized if N can be optimized for network planning.

The frequency reuse rate q is defined as: q ═ D/R ═ 3N)^1/2；

In the formula, D is a frequency multiplexing distance, namely the distance between adjacent co-frequency base stations; and R is the cell radius.

It can be seen that the cellular system capacity is determined by the frequency reuse rate q.

Frequency reuse necessarily causes mutual interference, i.e., co-channel interference. The closer the distance D between adjacent co-frequency base stations, the smaller the frequency reuse rate q, the larger the cellular system capacity, the higher the frequency utilization rate, but the larger the co-frequency interference. Co-channel interference mainly has 4 interference modes, as shown in fig. 2 to 5. Wherein, BS is base station, SS is user station; TX denotes a transmitting module, and RX denotes a receiving module; and assume that SS1 belongs to BS1 and SS2 belongs to BS 2.

The magnitude of the interference power depends on the effective transmit power, the multiplexing distance and the path attenuation. In existing cellular systems, sophisticated power control techniques are typically employed to reduce co-channel interference. Therefore, the prior art requires complex network planning and complex power control techniques.

Disclosure of Invention

In view of the above problems in the prior art, an object of the present invention is to provide a wireless communication system with reduced frequency reuse rate, so as to effectively reduce co-channel interference in the wireless communication system and simplify a network planning scheme.

The purpose of the invention is realized by the following technical scheme:

the invention provides a receiver for reducing frequency reuse rate, which comprises:

a set of receiving antennas: used for receiving each signal;

interference suppression and cancellation unit: the system is used for suppressing and counteracting the interference among the signals received by the group of receiving antennas;

a signal reception processing unit: the signal processing unit is used for carrying out channel decoding, symbol demapping and demodulation processing on the signal output by the interference suppression and cancellation unit;

the interference suppression and cancellation unit comprises:

a set of interference suppression and cancellation subunits: the interference suppression and cancellation subunits are arranged between a demodulator of the signal receiving and processing unit and the group of receiving antennas and are respectively used for processing each path of signal before demodulation to obtain each path of independent receiving signal, the interference suppression and cancellation subunits are sequentially connected in series, and the number of input signal paths of the interference suppression and cancellation subunits is sequentially reduced to obtain one path of signal of the receiving signal after the last processing;

or,

an interference suppression and cancellation subunit: and the signal processing unit is arranged between the demodulator of the signal receiving and processing unit and the group of receiving antennas, and is used for processing each path of received signals before demodulation and directly outputting an effective signal.

The receiver for reducing the frequency reuse rate further comprises a space-time/space-frequency/space-time-frequency/space-multiplexing decoding unit corresponding to the transmitter end: the space-time/space-frequency/space-time-frequency/space-multiplexing decoding processing is carried out on the received signals.

The signal receiving and processing unit further comprises:

a demapping processing module: the demodulator is used for demodulating the signals which are demodulated by the demodulator;

a decoder: and the channel decoding processing is carried out on the signal after the demapping processing.

The receiver further comprises:

and the signal selection unit is connected with the output end of the signal receiving and processing unit and is used for selecting one path of signal from the received and correspondingly processed signals as an effective received signal.

The interference suppression and cancellation unit establishes settings for maximum likelihood ML decoding, linear algorithm decoding or non-linear algorithm decoding.

The invention also provides a wireless communication system for reducing the frequency reuse rate, which comprises a transmitter and a receiver for reducing the frequency reuse rate, wherein the transmitter sends signals subjected to channel coding, symbol mapping and modulation processing through transmitting antennas, and the receiver receives the signals sent by the transmitter through a set of receiving antennas and performs channel decoding, symbol demapping, demodulation, interference suppression and cancellation processing on the signals to obtain received signals;

the set of receive antennas: used for receiving each signal;

a signal reception processing unit: the system is used for carrying out channel decoding, symbol demapping and demodulation processing on the received signals of the group of receiving antennas;

interference suppression and cancellation unit: the device is used for suppressing and counteracting the interference among the received signals;

the interference suppression and cancellation unit comprises:

a set of interference suppression and cancellation subunits: the interference suppression and cancellation subunits are arranged between the decoder and the group of receiving antennas and are respectively used for processing each path of signal before demodulation to obtain each independent path of receiving signal, the interference suppression and cancellation subunits are sequentially connected in series, and the number of input signal paths of the interference suppression and cancellation subunits is sequentially reduced to obtain one path of signal of the receiving signal after the last processing;

or,

an interference suppression and cancellation subunit: and the receiving antenna is arranged between the demodulator and the group of receiving antennas and is used for processing each received signal before demodulation and directly outputting an effective signal.

The transmitter comprises at least two transmitters, and the receiver carries out interference suppression and cancellation processing on at least two paths of received signals.

Each transmitter comprises a single coding unit transmitter based on a bit level and/or a single coding unit transmitter based on a symbol level, and the structure of the receiver side is arranged corresponding to the structure of each transmitter.

The receiver comprises:

a simple interference suppression receiver or a multiple decoding unit interference suppression receiver based on bit level, a simple interference suppression receiver or a multiple decoding unit interference suppression receiver based on symbol level, a multiple decoding unit interference suppression receiver based on bit level mixing, based on symbol level mixing, and based on bit level and symbol level mixing.

The wireless communication system for reducing the frequency reuse rate comprises a base station and a subscriber station, and,

the base station transmitter adopts a common transmitter or a single coding unit transmitter, different base stations transmit simultaneously or in a time-sharing manner, the receiver adopts a simple interference suppression receiver or a multi-decoding unit interference suppression receiver, the subscriber station transmitter adopts a common transmitter or a single coding unit transmitter, and the subscriber station receiver adopts a simple interference suppression receiver or a multi-decoding unit interference suppression receiver;

or,

the base station adopts a common transmitter or a single coding unit transmitter as a base station transmitter, different base stations transmit in a time-sharing mode, the receiver adopts a simple interference suppression receiver or a multi-decoding unit interference suppression receiver, the subscriber station transmitter adopts a common transmitter or a single coding unit transmitter, and the subscriber station receiver adopts a common receiver or a single decoding unit receiver;

or,

the base station and the user station adopt a common transmitter or a single coding unit transmitter, the base station and the user station adopt a common receiver or a single decoding unit receiver, and different base stations transmit in a time-sharing mode and receive in a time-sharing mode.

The single coding unit transmitter includes:

a signal transmission processing unit: the system is used for carrying out channel coding, symbol mapping and modulation processing on signals;

space-time/space-frequency/space-time-frequency/space-multiplexing coding unit: the method is used for carrying out space-time/space-frequency/space-time-frequency/space-multiplexing coding processing on the signals before channel coding processing or after channel coding, symbol mapping or modulation processing.

The technical scheme provided by the invention can be seen that the realization of the invention can effectively overcome the existing same frequency interference, effectively shorten the multiplexing distance, reduce the frequency multiplexing rate and increase the capacity of a cellular system. Even all cells of the cellular system can use only one frequency without complex network planning and power control techniques.

That is, the present invention can improve the spectrum utilization rate by multiples without increasing the bandwidth and the antenna transmission power, thereby improving the capacity of the wireless communication system.

Drawings

FIG. 1 is a schematic diagram of BLAST;

fig. 2 to 5 are schematic diagrams of four co-channel interference scenarios in the prior art;

fig. 6 is a conventional transmitter of the prior art;

FIG. 7 is a conventional receiver of the prior art; FIGS. 8-11 are four types of single coding unit transmitters in the prior art;

FIGS. 12-15 are four prior art single decoding unit receivers;

fig. 16 is a source bit level simple interference suppression receiver provided by the present invention;

fig. 17 is a channel bit-level simple interference suppression receiver provided by the present invention;

fig. 18 is a source symbol level simple interference suppression receiver provided by the present invention;

fig. 19 is a channel symbol level simple interference suppression receiver provided by the present invention;

fig. 20 is another channel bit-level simple interference suppression receiver provided by the present invention;

fig. 21 is a source-bit-level multi-decoding-unit interference suppression receiver provided by the present invention;

fig. 22 is a channel bit-level multiple decoding unit interference suppression receiver provided by the present invention;

fig. 23 is a source symbol level multiple decoding unit interference suppression receiver provided by the present invention;

fig. 24 is a channel symbol level multiple decoding unit interference suppression receiver provided by the present invention;

fig. 25 is a channel bit-level and source symbol-level hybrid multi-decoding unit interference suppression receiver provided by the present invention;

fig. 26 is a diagram of another source symbol level multiple decoding unit interference suppression receiver provided by the present invention;

fig. 27 is a schematic structural diagram of an interference suppression and cancellation unit 1;

fig. 28 is a schematic structural diagram of an interference suppression and cancellation unit 2;

fig. 29 is a schematic structural diagram of a wireless communication system 1 according to the present invention;

fig. 30 is a schematic diagram of a wireless communication system according to the present invention;

fig. 31 is a schematic structural diagram of a wireless communication system provided in the present invention 3;

fig. 32 is a schematic structural diagram of a wireless communication system provided in the present invention 4;

fig. 33 is a schematic structural diagram 5 of a wireless communication system according to the present invention.

Fig. 34 is a schematic diagram of a transmitter of a BS1 based on space-time codes;

fig. 35 is a schematic diagram of a transmitter of BS2 based on space-time codes;

fig. 36 is a schematic diagram of a receiver of SS1 based on space-time codes;

fig. 37 is a block diagram of a receiver of SS2 based on space-time codes.

Detailed Description

The core of the invention is that the 4 kinds of co-frequency interference can be overcome by using MIMO and mixed space technology (for example, the combination of layered space multiplexing codes, space-time codes, space-frequency codes or space-time-frequency codes), the multiplexing distance can be effectively shortened, the frequency multiplexing rate can be reduced, the frequency utilization rate can be improved, and the capacity of a cellular system can be increased. Even all cells of the cellular system can use only one frequency without complex network planning and power control techniques.

The present invention relates to a general transmitter, a general receiver, a single coding unit transmitter, a single coding unit receiver, a simple interference suppression receiver and a multi-decoding unit interference suppression receiver in a wireless communication system for reducing frequency reuse rate, which will be separately described below.

The structure of the common transmitter is shown in fig. 6, and specifically includes:

the signal sending processing unit is used for carrying out channel coding, symbol mapping and modulation processing on the sent signal and sending the signal by a transmitting antenna;

the structure of the general receiver shown in fig. 7 specifically includes:

a signal receiving processing unit, which is used for carrying out channel decoding, symbol demapping and demodulation processing on the received signals of the receiving antenna;

the structure of the single coding unit transmitter shown in fig. 8 to 11 specifically includes:

the space-time/space-frequency/space-time-frequency/space-multiplexing coding unit is used for carrying out space-time/space-frequency/space-time-frequency/space-multiplexing coding on the information source signal to form Ti transmitting branches;

the signal sending processing unit is used for carrying out channel coding, symbol mapping and modulation processing on the sending signal and sending the sending signal;

depending on the position where the encoder is placed, there may be a single coding unit transmitter based on bit level, as shown in fig. 8 and 9, and a single coding unit transmitter based on symbol level, as shown in fig. 10 and 11; the minimum coding unit of the bit-level encoder is a bit, and the minimum coding unit of the symbol-level encoder is a symbol, for example, the minimum coding unit in fig. 10 may be a symbol mapped by a QAM symbol; the minimum unit of coding in fig. 11 may be an OFDM symbol after OFDM modulation.

For different transmission branches, the same or different channel coding, symbol mapping and modulation modes (e.g., OFDM, OFDMA, or spread spectrum) may be used;

as shown in fig. 12 to 15, the (fourth) single decoding unit receiver specifically includes:

a signal receiving and processing unit, configured to apply channel decoding, symbol demapping, and demodulation manners, such as OFDM demodulation, OFDMA demodulation, or spread spectrum demodulation, in the same mode or different modes to different receiving branches;

depending on the decoder placement, there may be a single decoding unit receiver based on bit level, such as fig. 12 and 13, a single decoding unit receiver based on symbol level, such as fig. 14 and 15; the minimum unit of decoding for the bit-level decoder is a bit and the minimum unit of decoding for the symbol-level decoder is a symbol, e.g., the minimum unit of decoding in fig. 14 may be a symbol before QAM symbol demapping; the minimum unit of coding in fig. 15 may be an OFDM symbol before OFDM demodulation.

The above-mentioned transmitter and receiver are prior art transmitters and receivers.

For a simple interference suppression receiver, the receiver provided by the present invention, as shown in fig. 16 to fig. 20, specifically includes:

a signal receiving and processing unit, which has Rq receiving antennas, receives different branch signals and adopts the channel decoding mode, the symbol demapping mode and the demodulation mode of the same mode or different modes, such as OFDM demodulation, OFDMA demodulation or spread spectrum demodulation;

the interference suppression and cancellation unit jointly performs interference suppression and cancellation on the q decoding branches to obtain q received signals subjected to interference suppression and cancellation, or obtain one-way received signals subjected to interference suppression and cancellation, as shown in fig. 20.

Depending on the location of the interference suppression and cancellation units, there may be a simple interference suppression receiver based on bit level, such as fig. 16, 17 or 20, or a simple interference suppression receiver based on symbol level, such as fig. 18 or 19.

A signal selection unit, configured to, after being processed by each unit of the receiver, select one channel of signal from the q channels of received signals as a useful received signal if the received signal is a received signal after q channels of interference suppression and cancellation, where a specific selection manner is not limited in the present invention; if the received signal after single-path interference suppression and cancellation is obtained, the signal selection unit is not needed.

As to the multi-decoding unit interference suppression receiver, the receiver provided by the present invention, as shown in fig. 21 to fig. 26, specifically includes:

a signal receiving and processing unit, which has R1+ ·+ Ri + ·+ Rq receiving antennas, receives different branch signals, and adopts a channel decoding method, a symbol demapping method, and a demodulation method, such as OFDM demodulation, OFDMA demodulation, or spread spectrum demodulation, in the same mode or in different modes;

a space-time/space-frequency/space-time-frequency/space-multiplexing decoding unit is arranged corresponding to the transmitter side, and q space-time/space-frequency/space-time-frequency/space-multiplexing decoding units are specifically arranged, wherein each decoding unit corresponds to R1, a. All decoding branches may adopt a kind of trellis decoding or block decoding, or a part of decoding branches may adopt trellis decoding, and another part of decoding receiving branches adopts block decoding; when decoding the received signal of the ith decoding branch, the signals of the other decoding branches are treated as interference signals. The space-time/space-frequency/space-time-frequency decoder of the receiver requires channel estimation of MIMO (multiple input multiple output), MISO (multiple input single output) or SIMO (single input multiple output).

Depending on the location of the decoding unit, there may be a multi-decoding unit interference suppression receiver based on bit level, such as fig. 21 or fig. 22, a multi-decoding unit interference suppression receiver based on symbol level, such as fig. 23, fig. 24 or fig. 26, a multi-decoding unit interference suppression receiver based on source bit level and channel bit level mixing, source symbol level and channel symbol level mixing, and bit level (source or signal) and symbol level (source or signal) mixing, such as fig. 25; the minimum unit of decoding for the bit-level decoder is a bit and the minimum unit of decoding for the symbol-level decoder is a symbol, e.g., the minimum unit of decoding in fig. 23 may be a symbol before QAM symbol demapping; the minimum unit of coding in fig. 24 may be an OFDM symbol before OFDM demodulation.

The interference suppression and cancellation unit is located after the space-time/space-frequency/space-time-frequency/space-multiplexing decoding unit, and not necessarily immediately after the space-time/space-frequency/space-time-frequency/space-multiplexing decoding unit, the q decoding branches jointly perform interference suppression and cancellation to obtain q received signals after interference suppression and cancellation, or obtain a received signal after single-path interference suppression and cancellation, as shown in fig. 26.

A signal selection unit, configured to, after being processed by each unit of the receiver, select one channel of signal from the q channels of received signals as a useful received signal if the received signal is a received signal after q channels of interference suppression and cancellation, where a specific selection manner is not limited in the present invention; if the received signal after single-path interference suppression and cancellation is obtained, the signal selection unit is not needed.

For the interference suppression and cancellation unit, in theory, ML (maximum likelihood) decoding can be used to obtain the maximum spatial diversity (Ri), but the decoding complexity is large. A suboptimal algorithm may also be employed: including linear algorithms such as Zero Forcing (ZF) algorithm and Minimum Mean Square Error (MMSE) algorithm, etc., and non-linear algorithms such as SUC (SUccessive Cancellation algorithm), OSUC (Ordered SUccessive Cancellation algorithm), i.e., ZF V-BLAST (zero forcing bell labs layered space-time structure), etc. The linear algorithm has low decoding complexity, but because useful information in a received signal is not fully utilized, the diversity degree obtained is only Ri-Ti +1 which is far lower than that of the ML method, and the space-time characteristic is poor (although the MMSE has better performance than ZF). Although the characteristics of the nonlinear method are inferior to those of the ML method, the decoding complexity is greatly lower than that of the ML method, and a good compromise is made between the performance and the complexity. In the non-linear approach, SUC performs only slightly better than the linear approach, while OSUC is far superior to the linear approach.

Suppose there are q channels of information sources x₁，...，x_qWhere the effective source is x_iI.e. the target signal that the receiver really wants to receive. The structure of the interference suppressing and canceling unit may adopt the structure shown in fig. 27, and the interference suppressing and canceling unit has q channels of outputsR is₁，...，r_qIf the interference suppression and cancellation units are respectively from the receiving antennas 1, 1.. and q, the interference suppression and cancellation units consist of q layers of interference suppression and cancellation subunits; wherein, the layer 1 interference suppression and cancellation subunit is responsible for inputting r by q routes₁，...，r_qIn, to solve out a pair of information sources x_qIs estimated signal x ^_qAnd subtracting the receiving contribution of the receiving antenna q from the received signals of the receiving antennas 1,.. q, and using the remaining signals as a layer 2 interference suppression and cancellation subunit. Repeating the processing procedure of the layer 1 interference suppression and cancellation subunit by the q layer interference suppression and cancellation subunit to finally obtain the pair information source x₁，...，x_qIs estimated signal x ^₁，...，x^_qThen, the signal selection unit behind it selects the target signal x ^_i。

The present invention can also adopt another structure of an interference suppression and cancellation unit as shown in fig. 28, the interference suppression and cancellation unit has q inputs r₁，...，r_qIf the signals are respectively from the receiving antennas 1, 1.. q, the interference suppression and cancellation unit only consists of 1 layer of interference suppression and cancellation subunits; the layer 1 interference suppression and cancellation subunit is responsible for inputting r by q routes₁，...，r_qIn the method, effective information source x is directly selected and solved_iTarget estimation signal x ^_i. The structure interference suppression and cancellation unit is only provided with a single receiving processing branch, so that the problem that q paths of subsequent receiving processing branches are needed after the structure interference suppression and cancellation unit is solved, and a signal selection unit is not needed to be arranged after the interference suppression and cancellation unit.

The following description will take as an example the application of the above-mentioned transmitters and receivers, in particular of the simple interference suppression receiver and the multi-decoding unit interference suppression receiver, in a wireless communication system, i.e. a base station and a subscriber station system.

The first implementation is shown in fig. 29 and 30:

the scheme is suitable for TDD and FDD modes; for the TDD scheme, the assumption of synchronization of network transmission for each mode is based.

The base station transmitter adopts a common transmitter as shown in fig. 6 or a single coding unit transmitter as shown in fig. 8 to fig. 11, and the base station receiver adopts a simple interference suppression receiver or a multi-decoding unit interference suppression receiver; the subscriber station transmitter employs a general transmitter as shown in fig. 6 or the single coding unit transmitter of fig. 8 to 11, and the subscriber station receiver employs a simple interference suppression receiver or a multi-decoding unit interference suppression receiver. Taking TDD as an example, see fig. 29 and 30, the case of fig. 29 does not exist in FDD; wherein t0, t1, tr, tk and tk +1 in the figures represent different times; TX denotes a transmitting module, and RX denotes a receiving module; the BS is a base station and the SS is a subscriber station, and it is assumed that SS1 belongs to BS1 and SS2 belongs to BS 2; DL is a downlink frame, and UL is an uplink frame; fig. 29 is a schematic diagram of a system for overcoming the interference shown in fig. 2 and 3, and fig. 30 is a schematic diagram of a system for overcoming the interference shown in fig. 4 and 5.

The second implementation is shown in fig. 31 and 32:

the scheme is based on the assumption that the network transmission of each mode is synchronous, and is suitable for a TDD mode.

The base station transmitter adopts a common transmitter as shown in fig. 6 or a single coding unit transmitter as shown in fig. 8 to fig. 11, and the base station receiver adopts a simple interference suppression receiver or a multi-decoding unit interference suppression receiver, and different base stations transmit in a time-sharing manner; the subscriber station transmitter employs a general transmitter as shown in fig. 6 or a single coding unit transmitter as shown in fig. 8 to 11, and the subscriber station receiver employs a simple interference suppression receiver or a multi-decoding unit interference suppression receiver.

Referring to fig. 31 and 32: fig. 31 is a schematic diagram of a system for overcoming the interference shown in fig. 2 and 3, and fig. 32 is a schematic diagram of a system for overcoming the interference shown in fig. 4 and 5.

A third implementation is shown in fig. 33:

the scheme is suitable for TDD and FDD modes; in the TDD scheme, the assumption of synchronization between transmission and reception of the network is based on each mode.

The base station adopts a common transmitter shown in fig. 6 or a single coding unit transmitter shown in fig. 8 to fig. 11, and the base station receiver adopts a simple interference suppression receiver or a multi-decoding unit interference suppression receiver, and different base stations transmit in a time-sharing manner; the subscriber station employs a general transmitter as shown in fig. 6 or a single coding unit transmitter as shown in fig. 8 to 11 and a general receiver as shown in fig. 7 or a single decoding unit receiver as shown in fig. 12 to 15.

Taking TDD as an example, refer to fig. 24, which is a schematic diagram of a system for overcoming the interference shown in fig. 2 and 3. Due to the synchronization of the network transceiving of each mode, the interference shown in fig. 4 and 5 is not introduced.

The following describes a specific implementation of the present invention with a space-time code as an example.

The embodiment is shown in fig. 34, 35, 36 and 37, and specifically includes:

space-time codes are mainly aimed at flat fading channels, whereas in practical high-speed data transmission systems the channel characteristics are usually frequency selective fading. OFDM (orthogonal frequency division multiplexing) technology can divide a frequency selective fading channel into a plurality of parallel correlated flat fading channels, thus exhibiting non-frequency selective fading on each carrier. One embodiment of the present invention uses a combination of space-time codes and orthogonal frequency division multiplexing techniques on an OFDM system.

Assuming adjacent co-channel base stations BS1 and BS2, subscriber station SS1 belongs to BS1, and SS1 is interfered by BS 2. An OFDM system based on simple space-time code technique of dual antenna transmit diversity, single antenna reception, as shown in fig. 16 and 18. There are 2 transmitting antennas at each base station transmitting end, which are at least λ/2 apart (λ is wavelength), i.e. the process of transmitting signals propagating in different paths should be approximately considered as mutually independent attenuation process, there are 2 receiving antennas at the receiving end of the subscriber station, and the space-time decoder of the receiver of this scheme needs multiple-input multiple-output (MIMO) channel estimation.

The signal source 1 (or the signal source 2) is subjected to channel coding/symbol mapping, then symbol-level simple space-time coding, the output two paths of signals are respectively subjected to OFDM modulation, and finally transmitting antennas 1 and 2 (transmitting antennas or 3 and 4) are used for transmitting.

Base station 1 space-time coder inputs paired symbols(s)₁，s₂) I.e. at time 0, the symbol s₁And s₂Transmitting from antenna 1 and antenna 2, respectively; at time 1, the symbol (-s)₂A and(s)₁One) are transmitted from antenna 1 and antenna 2, respectively. Base station 2 space-time coder inputs paired symbols (x)₁，x₂) I.e. at time 0, the symbol x₁And x₂Transmitting from antenna 1 and antenna 2, respectively; at time instant 1, the symbol (-x)₂X and (x)₁One) are transmitted from antenna 3 and antenna 4, respectively. Where (#) represents a complex conjugate. Therefore, the symbol to be transmitted can be ensured to have an orthogonal space-time structure, and complete time domain diversity is formed.

The receiving signals of the two antennas of the receiver of the user station 1 are respectively demodulated by OFDM, the output two OFDM signals are respectively subjected to symbol-level simple space-time decoding, then pass through an interference suppression and cancellation unit, a pure BS1 signal and a pure BS2 signal are output, then channel decoding/symbol demapping is respectively carried out, and finally a BS1 signal is obtained by selection. The receiver structure of the subscriber station 2 is simpler, two paths of received signals are respectively subjected to OFDM demodulation, the output two paths of OFDM signals are respectively subjected to symbol-level simple space-time decoding, then are directly output pure BS2 signals through an interference suppression and cancellation unit, and then are subjected to channel decoding/symbol demapping to obtain BS2 signals.

In each receiving branch, the space-time decoder performs space-time linear combination on the received signals according to the following formula to obtain rank diversity of Ti × Ri (in this example, Ti is 2, Ri is 1):

$\left[\begin{array}{c}{r}_n\left(0\right)\\ {r_n}^{*}\left(1\right)\end{array}\right]=\sqrt{\frac{2}{N_T}}\left[\begin{array}{cccc}{h}_{n1}& -h_{n2}& h_{n3}& -h_{n4}\\ {{\mathrm{<figure-callout\; id="2"\; label="h\; n"\; filenames="C20051008072500204.png,C20051008072500205.png"\; state="\{\{state\}\}">h</figure-callout>}}_n}^{*}& {{\mathrm{<figure-callout\; id="1"\; label="h\; n"\; filenames="C20051008072500203.png,C20051008072500243.png"\; state="\{\{state\}\}">h</figure-callout>}}_n}^{*}& {h_{n4}}^{*}& {h_{n3}}^{*}\end{array}\right]\left[\begin{array}{c}{s}_1\\ {{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="C20051008072500204.png,C20051008072500205.png"\; state="\{\{state\}\}">s</figure-callout>}}_2}^{*}\\ x_1\\ {x_2}^{*}\end{array}\right]+\left[\begin{array}{c}{w}_n\left(0\right)\\ {w_n}^{*}\left(1\right)\end{array}\right];$

wherein h is_ijChannel coefficients for transmit antenna j to receive antenna i, the result of a multiple-input multiple-output (MIMO) channel estimation; w is a_i(t) Additive White Gaussian Noise (AWGN) satisfying normal distribution; coefficient (2/N)_T)^1/2For normalizing the transmit power; n is a radical of_TThe number of transmit antennas, in this case equal to the sum of the two base station transmit antennas 4; n is 1 or 2.

In summary, the implementation of the present invention can overcome the co-channel interference shown in fig. 2 to fig. 5, effectively shorten the multiplexing distance, reduce the frequency multiplexing rate, and increase the cellular system capacity. Even all cells of the cellular system can use only one frequency without complex network planning and power control techniques.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (11)

1. A receiver for reducing frequency reuse, comprising:

a set of receiving antennas: used for receiving each signal;

interference suppression and cancellation unit: the system is used for suppressing and counteracting the interference among the signals received by the group of receiving antennas;

a signal reception processing unit: the signal processing unit is used for carrying out channel decoding, symbol demapping and demodulation processing on the signal output by the interference suppression and cancellation unit;

the interference suppression and cancellation unit comprises:

a set of interference suppression and cancellation subunits: the interference suppression and cancellation subunits are arranged between a demodulator of the signal receiving and processing unit and the group of receiving antennas and are respectively used for processing each path of signal before demodulation to obtain each path of independent receiving signal, the interference suppression and cancellation subunits are sequentially connected in series, and the number of input signal paths of the interference suppression and cancellation subunits is sequentially reduced to obtain one path of signal of the receiving signal after the last processing;

or,

an interference suppression and cancellation subunit: and the signal processing unit is arranged between the demodulator of the signal receiving and processing unit and the group of receiving antennas and is used for processing each received signal before demodulation and directly outputting an effective signal.

2. The receiver according to claim 1, further comprising a space-time/space-frequency/space-time-frequency/space-multiplexing decoding unit corresponding to the transmitter, disposed between the set of receiving antennas and the interference suppressing and canceling unit, respectively connected to the set of receiving antennas and the interference suppressing and canceling unit, and configured to perform space-time/space-frequency/space-time-frequency/space-multiplexing decoding processing on signals received by the set of receiving antennas.

3. The receiver according to claim 1 or 2, wherein the signal reception processing unit further comprises:

a demapping processing module: the demodulator is used for demodulating the signals which are demodulated by the demodulator;

a decoder: and the channel decoding processing is carried out on the signal after the demapping processing.

4. The reduced frequency reuse receiver according to claim 3, wherein said receiver further comprises:

and the signal selection unit is connected with the output end of the signal receiving and processing unit and is used for selecting one path of signal from the received and correspondingly processed signals as an effective received signal.

5. The receiver of claim 3, wherein the interference suppression and cancellation unit is configured to establish the setting based on Maximum Likelihood (ML) decoding, linear algorithm decoding, or non-linear algorithm decoding.

6. A wireless communication system for reducing frequency reuse rate is characterized by comprising a transmitter and a receiver for reducing frequency reuse rate, wherein the transmitter transmits signals subjected to channel coding, symbol mapping and modulation processing through transmitting antennas, and the receiver receives the signals transmitted by the transmitter through a set of receiving antennas and performs channel decoding, symbol demapping, demodulation, interference suppression and cancellation processing on the signals to obtain received signals;

the receiver includes: interference suppression and cancellation unit: the device is used for suppressing and counteracting the interference among the received signals;

the interference suppression and cancellation unit comprises:

a set of interference suppression and cancellation subunits: the interference suppression and cancellation subunits are arranged between the demodulator and the group of receiving antennas and are respectively used for processing each path of signal before demodulation to obtain each path of independent receiving signal, the interference suppression and cancellation subunits are sequentially connected in series, and the number of input signal paths of the interference suppression and cancellation subunits is sequentially reduced to obtain one path of signal of the receiving signal after the last processing;

or,

an interference suppression and cancellation subunit: and the receiving antenna is arranged between the demodulator and the group of receiving antennas and is used for processing each received signal before demodulation and directly outputting an effective signal.

7. The wireless communication system according to claim 6, wherein the transmitter comprises at least two, and the receiver performs interference suppression and cancellation on at least two received signals.

8. The wireless communication system according to claim 6 or 7, wherein each transmitter comprises a single coding unit transmitter based on bit level and/or a single coding unit transmitter based on symbol level, and the receiver-side structure is arranged corresponding to each transmitter structure.

9. The wireless communication system of claim 8, wherein the receiver comprises:

a simple interference suppression receiver or a multiple decoding unit interference suppression receiver based on bit level, a simple interference suppression receiver or a multiple decoding unit interference suppression receiver based on symbol level, a multiple decoding unit interference suppression receiver based on bit level mixing, based on symbol level mixing, and based on bit level and symbol level mixing.

10. The wireless communication system for reducing frequency reuse rate according to claim 6 or 7, comprising a base station and a subscriber station, and,

the base station transmitter adopts a common transmitter or a single coding unit transmitter, different base stations transmit simultaneously or in a time-sharing manner, the receiver adopts a simple interference suppression receiver or a multi-decoding unit interference suppression receiver, the subscriber station transmitter adopts a common transmitter or a single coding unit transmitter, and the subscriber station receiver adopts a simple interference suppression receiver or a multi-decoding unit interference suppression receiver;

or,

the base station transmitter adopts a common transmitter or a single coding unit transmitter, different base stations transmit in a time-sharing manner, the receiver adopts a simple interference suppression receiver or a multi-decoding unit interference suppression receiver, the subscriber station transmitter adopts a common transmitter or a single coding unit transmitter, and the subscriber station receiver adopts a common receiver or a single decoding unit receiver;

or,

the base station and the user station adopt a common transmitter or a single coding unit transmitter, the base station and the user station adopt a common receiver or a single decoding unit receiver, and different base stations transmit in a time-sharing mode and receive in a time-sharing mode.

11. The wireless communication system of claim 10, wherein the single coding unit transmitter comprises:

a signal transmission processing unit: the system is used for carrying out channel coding, symbol mapping and modulation processing on signals;

space-time/space-frequency/space-time-frequency/space-multiplexing coding unit: the method is used for carrying out space-time/space-frequency/space-time-frequency/space-multiplexing coding processing on the signals before channel coding processing or after channel coding, symbol mapping or modulation processing.

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