The present invention relates to, particularly, a scalable bandwidth system, wireless base station and wireless terminal apparatus that carry out multicarrier communication by assigning on a per terminal basis flexibly a bandwidth less than a plurality of maximum bandwidths supported by the wireless base station apparatus as a communication band for each wireless terminal apparatus.
Conventionally, upon carrying out multicarrier communication represented by the OFDM (Orthogonal Frequency Division Multiplexing) scheme, a wireless communication system is proposed for supporting a plurality of maximum bandwidths at the wireless base station (hereinafter, simply a “base station”) and enabling flexible assignment of bandwidths used for actual communication from the maximum bandwidths by each wireless communication terminal (hereinafter, simply a “terminal”). Such a wireless communication system is referred to as a “scalable bandwidth system.”
An overview of this scalable bandwidth system will be described with reference to
By the way, in this scalable bandwidth system, when each terminal carries out initial cell search such as symbol synchronization using a random frequency band and sets up communication independently, as shown in
Conventionally, the technique disclosed in Non-Patent Document 1 is disclosed as a method to solve such a problem. In Non-Patent document 1, as shown in
To be more specific, the terminal acquires cell synchronization using a synchronization channel arranged in a band (in
In this way, by using the technique disclosed in Non-Patent Document 1, the communication band for the terminal can be assigned according to control by the base station compared to the case where a terminal determines a communication band for the terminal itself independently, so that it is assumed to be able to reduce unbalance in traffic in the maximum bandwidth.
Non-Patent Document 1: “Physical layer items not for inclusion in Release 99,” TR 25.833, 3GPP TSG RAN WG1, NTT DoCoMo, Inc.
However, even if the technique of Non-Patent Document 1 is used, it is not enough to reduce unbalance in traffic. For example, although there are a variety of terminals with variant bandwidth capabilities in a cell (for example, there is a terminal with bandwidth capability of 1.25 MHz or a terminal with bandwidth capability of 2.5 MHz), a method for reducing unbalance in traffic under such conditions is not sufficiently studied.
It is therefore an object of the present invention to provide a scalable bandwidth system, wireless base station apparatus and wireless terminal apparatus that, when there are a variety of terminals with variant bandwidth capabilities in a cell, can reduce unbalance in traffic in the maximum bandwidth.
The scalable bandwidth system according to the present invention that carries out multicarrier communication by assigning on a per terminal basis flexibly bandwidths less than a plurality of maximum bandwidths supported by a radio base station apparatus as a communication band of each radio terminal apparatus, adopts a configuration including: a base station apparatus that transmits a synchronization signal for cell synchronization in a band determined in advance from the maximum bandwidths; and a wireless terminal apparatus that, after acquiring cell synchronization using the received synchronization signal, transmits an identification signal of the wireless terminal apparatus and bandwidth capability information of the wireless terminal apparatus, to the wireless base station apparatus.
According to this configuration, the wireless base station apparatus is able to assign a band to each terminal taking into account the bandwidth capability of each terminal in a cell, so that it is possible to reduce unbalance in traffic in the maximum bandwidth.
The scalable bandwidth system according to the present invention that carries out multicarrier communication by assigning on a per terminal basis flexibly bandwidths less than bandwidths of a plurality of maximum bandwidths supported by a wireless base station apparatus as a communication band of each wireless terminal apparatus, adopts a configuration including: a wireless base station apparatus that transmits a synchronization signal for cell synchronization in a band determined in advance from the maximum bandwidths and reports information of a plurality of candidate bands unique to a cell of the wireless base station apparatus using a shared channel in the same band as the determined band, to each wireless terminal apparatus; and a wireless terminal apparatus that selects a communication band with a bandwidth matching bandwidth capability of the wireless terminal apparatus from the candidate bands and carries out communication using the communication band.
According to this configuration, a terminal selects a communication band used for the terminal itself only from candidate bands designated by the base station, so that, compared to the case where the terminal selects a communication band at random from the maximum bandwidth, it is possible to reduce unbalance in traffic in the maximum bandwidth.
The scalable bandwidth system according to the present invention that carries out multicarrier communication by assigning on a per terminal basis flexibly bandwidths less than a plurality of maximum bandwidths supported by a wireless base station apparatus as a communication band for each wireless terminal apparatus, adopts a configuration including a wireless base station apparatus that transmits a synchronization signal for cell synchronization in a band determined in advance from the maximum bandwidths and transmits congestion information for used subcarriers from the maximum bandwidths; and a wireless terminal apparatus that selects a communication band based on the congestion information and bandwidth capability of the wireless terminal apparatus and carries out communication using this communication band.
According to this configuration, a terminal is able to select a less congested band as a communication band of the terminal itself based on congestion information, so that it is possible to disperse traffic in the maximum bandwidth and reduce unbalance in traffic.
According to the present invention, even when there are a variety of terminals with variant bandwidth capabilities in a cell, it is possible to realize a scalable bandwidth system, wireless base station apparatus and wireless terminal apparatus that can reduce unbalance in traffic in the maximum bandwidth.
Hereinafter, embodiments of the present information will be described in detail with reference to the accompanying drawings.
Similar to a base station of a general scalable bandwidth system, base station 100 assigns on a per terminal basis flexibly a bandwidth less than a plurality of the maximum bandwidths supported by the base station as a communication band of each terminal and carries out OFDM communication between the base station and each terminal.
Further, in this embodiment, base station 100 transmits a synchronization code (synchronization signal) and band assignment information to each terminal from a band (in this embodiment, a band (for example, 5 MHz) of the central portion of the maximum bandwidth) determined in advance in a cell.
First, the configuration of base station 100 shown in
Coding section 102 carries out error correction coding of data inputted from transmission controlling section 101 and sends out obtained encoded data to modulating section 103. Modulating section 103 carries out modulation processing such as QPSK (Quadrature Phase Shift Keying) and 16QAM (Quadrature Amplitude Modulation) of encoded data and sends out the obtained modulated signal to frame shaping section 104. Frame shaping section 104 shapes a transmission frame signal by adding the pilot signal (PL) to the modulated signal and sends out this signal to scrambling section 105. Scrambling section 105 carries out scrambling processing using a scrambling code unique to a cell and sends out the scrambled signal to subcarrier assigning section 106.
Subcarrier assigning section 106 assigns signals corresponding to transmission data 1 to n from signals for each terminal after scrambling processing, to subcarriers matching band assignment information, based on band assignment information of each terminal from band assigning section 120. In contrast with this, subcarrier assigning section 106 assigns signals matching band assignment information of each terminal from signals for each terminal after scrambling processing, to a band of the central portion of the maximum bandwidth. Similarly, subcarrier assigning section 106 assigns the inputted synchronization code to the band of the central portion of the maximum bandwidth upon cell search. Further, subcarrier assigning section 106 is formed with a serial-to-parallel conversion circuit.
Output of subcarrier assigning section 106 is processed at inverse fast Fourier transform section (IFFT) 107, is inserted a cyclic prefix (CP) at subsequent cyclic prefix inserting section 108, is subjected to predetermined radio processing such as digital-to-analogue conversion processing at radio transmitting section 109 and up-conversion to radio frequency and, then, is outputted from antenna 110.
Next, the receiving system of base station 100 will be described. Base station 100 inputs a signal received at antenna 110 to radio receiving section 111. The received signal is subjected to predetermined radio processing such as down-conversion and analogue-to-digital conversion processing at radio receiving section 111 to a baseband OFDM signal, is removed the cyclic prefix portion by CP removing section 112 and is inputted to fast Fourier transform section (FFT) 113. The signal subjected to a fast Fourier transform by FFT 113 is inputted to baseband processing units 114-1 to 114-n equaling the number of terminals.
The configurations of baseband processing units 114-1 to 114-n are the same, and so the configuration of one unit alone is shown in
Band assigning section 120 inputs terminal identification information (UE-ID) of each terminal, bandwidth capability information (UE bandwidth capability) of each terminal and frequency assignment request information of each terminal transmitted from terminals 1 to n from received data and assigns a communication band to each terminal based on these items of information. In this way, base station 100 assigns a communication band to each terminal using bandwidth capability information reported from each terminal, so that it is possible to carry out band assignment processing such that unbalance in traffic in the maximum bandwidth supported by the base station does not occur.
Band assignment information for terminals 1 to n obtained by band assigning section 120 is transmitted to terminals 1 to n as described above immediately after initial cell search is completed. Further, band assignment information is inputted to subcarrier assigning section 106, and is used as a control signal for controlling as to which subcarriers transmission signals for terminals 1 to n are assigned and transmitted.
Next, the configuration of terminal 200 shown in
Coding section 202 carries out error correction coding of data inputted from transmission controlling section 201 and sends out obtained encoded data to modulating section 203. Modulating section 203 carries out modulation processing such as QPSK and 16QAM of encoded data and sends out the obtained modulated signal to subcarrier assigning section 204.
Subcarrier assigning section 204 assigns a signal corresponding to transmission data from modulated signals, to subcarriers matching band assignment information, based on band assignment information for terminal 200 that is extracted from band assignment information extracting section 222. In contrast with this, subcarrier assigning section 204 assigns a signal matching UE-ID information, UE bandwidth capability information and frequency band assignment request information from the modulated signals, to a band of the central portion of the maximum bandwidth (that is, the same band as the band where a synchronization signal and band assignment information are transmitted by base station 100). Further, subcarrier assigning section 204 is formed with a serial-to-parallel conversion circuit.
Output of subcarrier assigning section 204 is processed at inverse fast Fourier transform section (IFFT) 205, is inserted a cyclic prefix at subsequent cyclic prefix (CP) inserting section 206, is subjected to predetermined radio processing such as digital-to-analogue conversion processing and up-conversion to radio frequency at radio transmitting section 207 and, then, is outputted from antenna 208.
Next, the receiving system of terminal 200 will be described. Terminal 200 inputs a signal received at antenna 208 to radio receiving section 211. Radio receiving section 211 carries out radio processing such as down-conversion and analogue-to-digital conversion processing of a received signal and obtains a baseband OFDM signal. Further, radio receiving section 211 outputs only an OFDM signal of a band (subcarrier) assigned to terminal 200, based on band assignment information extracted by band assignment information extracting section 222.
The baseband OFDM signal outputted from radio receiving section 211 is removed the cyclic prefix at cyclic prefix removing section (CP removing section) 212 and is inputted to fast Fourier transform section (FFT) 213. Further, the baseband OFDM signal is inputted to symbol timing detecting section 214. Symbol timing detecting section 214 calculates a correlation value between the original portion of the cyclic prefix of the baseband OFDM signal and the cyclic prefix portion of a signal with an offset of an effective symbol length from the OFDM signal, and detects the symbol timing by detecting the peak of this correlation value. By carrying out FFT processing at the symbol timing (FFT window timing) detected at symbol timing detecting section 214, FFT 213 obtains the signal before IFFT processing, and sends out this signal to descrambling section 215, synchronization code correlation calculating section 216 and pilot correlation calculating section 217.
Synchronization code correlation calculating section 216 calculates a correlation value between a signal outputted from FFT 213 and a replica of the synchronization code and sends out the correlation value to frame timing/code group detecting section 218. By detecting the peak of the correlation value, frame timing/code group detecting section 218 detects the frame timing and code group. Pilot correlation calculating section 217 calculates the correlation value between the signal outputted from FFT 213 and a plurality of candidate scramble codes (that is, the correlation value between the pilot arranged at the frame head and subjected to scrambling processing, and a plurality of candidate scrambling codes) and sends out the correlation value to scrambling code identifying section 219. Scrambling code identifying section 219 identifies that the scramble code with the maximum correlation value is the scramble code used in base station 100 and sends out the identified scramble code to descrambling section 215. Descrambling section 215 descrambles the signal outputted from FFT 213 using the identified scrambling code. Received data is obtained by demodulating the descrambled signal at demodulating section 220 and decoding the signal at decoding section 221.
Band assignment information extracting section 222 extracts band assignment information transmitted from base station 200 for terminal 200 from received data and sends out this band assignment information to subcarrier assigning section 204 and radio receiving section 211. In this way, terminal 200 transmits a signal by assigning the signal to the subcarrier matching band assignment information indicated from base station 100 and carries out reception processing of the signal assigned to the subcarrier matching band assignment information.
Next, operation of terminal 200 and base station 100 of this embodiment will be described with reference to
In step ST1, terminal 200 carries out initial cell search using a synchronization signal (synchronization code) arranged on the central portion of the maximum bandwidth. Next, after initial cell search is completed, terminal 200 transmits UE-ID information of terminal 200, UE bandwidth capability information and frequency band assignment request, to the searched cell (base station 100). Terminal 200 transmits these items of information using the frequency of the central portion of the maximum bandwidth or the frequency that makes a pair of the frequency of the central portion of the maximum bandwidth.
When receiving UE-ID, UE bandwidth capability and frequency band assignment request, in step ST2, by referring to the bandwidth capability of a terminal at band assigning section 120, base station 100 assigns the communication band (the center frequency and bandwidth) to the terminal and reports this assignment information to this terminal. In this case, base station 100 forms a shared channel embedded with UE-ID and band assignment information and transmits this shared channel using the central portion of the maximum bandwidth (that is, the same band as the band subjected to cell search by the terminal). Terminal 200 decodes band assignment information for terminal 200 in this shared channel, and, in step ST3, carries out shifting such that the frequency for use (that is, the assigning band at subcarrier assigning section 204 and a passband at radio receiving section 211) matches band assignment information.
Band assignment information is formed with center frequency information and bandwidth information.
As described above, according to this embodiment, terminal 200 transmits bandwidth capability information of terminal 200 and base station 100 assigns a communication band on a per terminal basis, based on an identification signal and bandwidth capability information transmitted from terminal 200 and transmits communication band information of each assigned terminal using a shared channel, so that, even when there are a variety of terminals with variant bandwidth capabilities in a cell, it is possible to realize a scalable bandwidth system that is able to reduce unbalance in traffic in the maximum bandwidth.
Embodiment 1 proposes that the terminal reports bandwidth capability of the terminal to the base station, and the base station assigns a communication band of each terminal by referring to bandwidth capability of each terminal and indicates assigned communication band information of each terminal using the shared channel, so that unbalance in traffic is reduced in the maximum bandwidth.
In contrast with this, Embodiment 2 proposes that a base station indicates candidate band information to each terminal using such as a common channel and a terminal selects a band matching bandwidth capability of the terminal from this candidate band information, so that unbalance in traffic is reduced in the maximum bandwidth.
First, the configuration of base station 300 will be described with reference to
Candidate band information generating section 302 inputs selected band information (UE selected band) selected by each terminal and generates candidate band information based on this information. To be more specific, candidate band information generating section 302 generates candidate band information from which bands already selected by a given terminal or bands already selected by many terminals are removed.
Next, the configuration of the terminal will be described with reference to
Terminal 400 has candidate band information extracting section 402. Candidate band information extracting section 402 extracts candidate band information transmitted in common to each terminal from base station 300, from received data and sends out candidate band information to band selecting section 403. Band selecting section 403 selects a band matching band width capability of terminal 400 from candidate bands and sends out the selected band to transmission controlling section 401 as UE selected band information.
Next, operation of base station 300 and terminal 400 of this embodiment will be described.
Here, in the scalable bandwidth system of this embodiment, band assignment provided to terminal 400 is as shown in
Further, for example, when bandwidth capability of terminal 400 is 1.25 MHz and there are a plurality of center frequency information where the bandwidth is used as candidate bands as shown in
Further, when a band is congested after communication setup and when traffic becomes unbalanced due to random selection, by transmitting to several terminals dedicated control information for shifting the band to bands of the same bandwidth, it is possible to reduce unbalance in traffic.
By the way, base station 300 may monitor which band is selected by each terminal in a cell and change candidate band information depending on the time according to the condition. For example, if a band is selected at one time by many bands, when candidate band information is reported the next time, candidate band information from which the band is removed is reported. In this way, it is possible to further reduce unbalance in traffic.
As described above, according to this embodiment, base station 300 transmits candidate band information using, for example, the common channel to each terminal and terminal 400 selects a band matching bandwidth capability of terminal 400 from this candidate band information, so that, compared to the case where a terminal selects a communication band from the maximum bandwidth at random, it is possible to reduce unbalance in traffic in the maximum bandwidth. Further, compared to Embodiment 1, if terminal 400 does not report bandwidth capability information of terminal 400, terminal 400 obtains band information where terminal 400 is applicable. In this way, if less uplink signaling for reporting bandwidth capability information of terminal 400 is not used, it is possible to save more radio resources.
Next, operation of terminal 600 and base station 500 of this embodiment will be described with reference to
First, when receiving the synchronization channel from base station 500, in step ST11, terminal 600 carries out initial cell search using a synchronization signal (synchronization code) arranged on the central portion of the maximum bandwidth. Next, when receiving congestion information, in step ST12, terminal 600 selects a band according to congestion information and bandwidth capability of terminal 600. In step ST13, terminal 600 shifts the band for use to the selected band (to be more specific, adjusts a function of subcarrier assigning section 204 and radio receiving section 211 to the selected band). Further, in step ST14, base station 500 updates congestion information according to terminal band selection result information reported from terminal 600 and indicates this congestion information to terminal 600.
In this way, base station (or upper controlling apparatus) 500 manages congestion information of each current subcarrier (or raster or subcarrier block) and indicates congestion information of each subcarrier (or raster or subcarrier block) to terminal 600. Terminal 600 selects a band for use based on this congestion information. Terminal 600 reports the selected band to base station 500. Base station 500 updates congestion information based on selection information reported from terminal 600. Base station 500 transmits updated information as reporting information. Congestion information is generated by calculating, for example, the number of terminals that are currently in use or the level of congestion of each subcarrier, raster or subcarrier block.
As described above, according to this embodiment, base station 500 indicates congestion information to each terminal and terminal 600 selects a less congested band as the band for use of terminal 600 based on congestion information, so that it is possible to disperse traffic in the maximum bandwidth and reduce unbalance in traffic.
The present application is based on Japanese patent application No. 2005-246653, filed on Aug. 26, 2005, the entire content of which is expressly incorporated by reference herein.
The scalable bandwidth system, wireless base station apparatus and wireless terminal apparatus according to the present invention can be applied to a scalable bandwidth system, wireless base station apparatus and wireless terminal apparatus that, even when there are a variety of terminals with variant bandwidth capabilities in the maximum bandwidth, can reduce unbalance in traffic in the maximum bandwidth.
Number | Date | Country | Kind |
---|---|---|---|
2005-246653 | Aug 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP2006/316411 | 8/22/2006 | WO | 00 | 2/24/2009 |