WO2013187753A2

WO2013187753A2 - System and method for dynamic spectrum access with coordinated primary user management

Info

Publication number: WO2013187753A2
Application number: PCT/MY2013/000104
Authority: WO
Inventors: Bin Mohamad @ Din HAFIZAL; Tahir MOHAMMAD; Ying Loong LEE; Binti Hashim WAHIDAH; Bin Ramli NORDIN
Original assignee: Mimos Berhad
Priority date: 2012-06-13
Filing date: 2013-05-23
Publication date: 2013-12-19
Also published as: MY156138A; WO2013187753A3

Abstract

The present invention provides a system for sending and detecting wireless communication links involving the utilization of coordinated access control channel by PU. The system includes a spectrum manager operationally modifies MAC frame based on a role of Primary User (PU) to improve the accuracy of he white space detection and allocates an appropriate spectrum to Secondary User (SU) and a spectrum sensing function (SSF) operatively sensing the spectrum for white space, whereby the SSF avoid sensing the whole spectrum of interest to reduce sensing time and overall complexity. Methods of coordinating access and sharing spectrums are also provided herewith.

Description

SYSTEM AND METHOD FOR DYNAMIC SPECTRUM ACCESS WITH COORDINATED PRIMARY USER MANAGEMENT

Field of the Invention

[0001] The present invention relates generally to wireless communication and more particularly to a system with coordinated primary user management for dynamic spectrum access and further to a method with a novel sensing and detection mechanism for dynamic spectrum access.

Background of the Invention

[0002] Scarce radio spectrum can be utilized more efficiently via Dynamic

Spectrum Access (DSA). DSA refers to a medium access strategy through which secondary users (SUs) can opportunistically communicate on a channel that is licensed to primary users (PUs). This secondary access takes place during spectrum whitespaces— · time intervals when the channel is free from transmission by its authorized licensees (i.e. PUs). Therefore, spectrum should be managed for efficient coexistence between PUs and SUs in order to avoid interference.

[0003] As shown in FIG 1 , the exemplified wireless communication system comprises a Base Station (BS), a plurality of PUs and a plurality of SUs, where the spectrum has n channels from f₁ to f_N. In FIG 1 (a), all channels are occupied by PUs; thus no channel is available for SUs; in FIG 1 (b), some channels are free from PUs; thus they are available for SUs; and in FIG 1 (c), all channels are available for SUs. The scenario in FIG 1 (b) is more common than the two others. Therefore, the coexistence of PUs and SUs has to be managed efficiently to avoid interference. Currently, DSA functions to allow a SU to opportunistically access the spectrum when the PU is not present/active. The accuracy to detect the available channel is subject to the information gathered by SU. However, the role of PU is not considered in current DSA as there is no such mechanism to perform this function. In addition, continuous scanning and sensing the whole spectrum of interest has the following drawbacks: (i) a considerable time to complete in which the spectrum opportunity may be lost; and (ii) high complexity in terms of processor, analog to digital converter, memory, power consumption and hardware implementation.

Summary of the invention

[0004] One aspect of the present invention provides a system for sending and detecting wireless communication links involving the utilization of coordinated access control channel by PU. A spectrum manager operationally modifies MAC frame based on a role of Primary User (PU) to improve the accuracy of he white space detection and allocates an appropriate spectrum to Secondary User (SU) and a spectrum sensing function (SSF) operatively sensing the spectrum for white space are provided. The SSF avoid sensing the whole spectrum of interest to reduce sensing time and o verall complexity.

[0005] In one embodiment, the modified MAC frame comprises a user ID of the

PU BS who broadcast the message on control channel; a CH ID for determining fi-ee channels allocable for SU; power information of the transmission that indicating allowable transmit power as one restricted condition for SU to operated using CH ID contrails; a channel occupancy; release code to grant channel access to PU when primary user wish to come back again for transmission. The free channels may include frequency and/or bandwidth. It is also possible that the channel occupancy includes channel usage statistics, channel occupancy probability, user arrival probability in further and holding time.

[0006] In another aspect, the present invention provides a method for coordinating access among primary and secondary users in a wireless network. The method comprises initiating network entry process for PU, by communicating with the base station (BS) to connect with a selected wireless network; recognizing all PU in the network by sending control paging channel; receiving response from PU within the BS range; classifying active and idle PU by monitoring communication links and analyze a utilization pattern; checking available spectrum within cells by detecting the idle and busy channel; broadcasting available channels for SU by transmitting band access control channel (BACC) to all SU; checking BACC within frequency band of interest for SU to determine instantaneous channels availability; providing link condition parameters; deciding to utilize the available channel and transmit data to other SU; determining whether SU receives release code from PU; detecting BACC with a release code signal specifying a time that the channel be vacated; and ceasing operation by the SU in PU frequency band and using default sensing mechanism to detect white space. The important link condition parameter may include channel bandwidth, allowable power, channel occupancy probability.

[0007] In yet another aspect, the present invention may further provide a method for sharing spectrum among secondary users. The method comprises receiving BACC; performing additional sensing by SU based on available band information obtained from BS; communicating with nearby SU for available band mitigating an effect of shadowing or fading encountered during BACC reception based on the sensing result; checking and determining if the detected available channel power is below a prescribed threshold; and negotiating an usage of the available bands based on application requirements by SU, wherein user with more bandwidth requirement can be assigned with more bandwidth.

[0008] One objective of the present invention is to allow secondary user (SU) to transmit signal wirelessly when the spectrum is not in use by primary users (PU); this will increase the spectrum utilization.

[0009] Another objective of the present invention is to increase the probability of detection (PD) and reduce the probability of false alarm (PFA) and avoid interference to PU in cognitive radio network.

[0010] Another objective of the present invention is to reduce sensing time and reduce the SU CR system complexity for dynamic spectrum access mechanism.

[0011] The objectives and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof in connection with the accompanying drawings. Brief Description of the Drawings

[0012] Preferred embodiments according to the present invention will now be described with reference to the Figures, in which like reierence numerals denote like elements.

[0013] FIG l shows an exemplified wireless communication system in the prior art.

[0014] FIG 2 shows an exemplified wireless communication system comprising base stations with band access control channels in accordance with one embodiment of the present invention. [0015] FIG 3 is a block diagram of the Base Station/Access point in accordance with one embodiment of the present invention.

[0016] FIG 4 illustrates the transmission of BACC to S U .

[0017] FIG 5 shows an exemplary frame format of BACC in accordance with one embodiment of the present invention,

[0018] FIG 6 is a block flowchart of the method of coordinated sensing and detection with BACC in accordance with one embodiment of the present invention.

[0019] FIG 7 is a block flowchart of the sensing and detection by the SSF in accordance with one embodiment of the present invention,

[0020] FIGs 8-9 are graphs showing the simulation results.

Detailed Description of the Invention

[0021] The present invention may be understood more readily by reference to the following detailed description of certain embodiments of the invention.

[0022] Throughout this application, where publications are referenced, the disclosures of these publications are hereby incorporated by reference, in their entireties, into this application in order to more fully describe the state of art to which this invention pertains.

[0023] The present invention provides a system including a spectrum manager for better managing the coexistence of PUs and SUs, In brief, the spectrum manager is embedded in the Medium Access Control (MAC) layer of a BS/access point, where the spectrum manager comprises a Band Access Control Channel (BACC) to control and coordinate PUs and SUs operating in the licensed band. The BACC can be used as both data and control channel. When a PU has no channel free, the BACC is absent. If there is any available channel then the BACC broadcasts the availability of channel periodically for the use by cognitive users (SUs); thus PU grants permission for SU to use his band when there is no active PU. This new sensing and detection mechanism embedded in the BACC considers the role of PUs so as to improve the accuracy of the white space detection and allow the right spectrum to be allocated to SUs.

[0024] The system of the present invention further comprises a Spectrum Sensing

Function (SSF) embedded in the PHY Layer of the BS/access point, where the SSF senses and provides information to S U for operation in other licensed bands, and it helps SUs to identify available band (i.e., PU assists SU). The SSF reduces the need for SU to scan the whole spectrum of interest and this will reduce sensing time and the overall complexity.

[0025] Referring now to FIG 3, there is provided a block diagram of the Base

Station/ Access point in accordance with one embodiment of the present invention. The BS 10 comprises a MAC layer and a PHY layer, where the MAC layer comprises the standard modules such as Ranging, Admission control, Connection identifier, QoS policy and Scheduler, and the PHY layer comprises the standard modules such as Modulation, Coding, STBC, Channel estimation and HARQ, CQI. These standard modules are well known in the art; thus no further details are provided for these standard modules in order not to obscure the present invention.

[0026] In one embodiment of the present invention, the BS 10 comprises a spectrum manager 11 for managing the spectrums accessed by the BS. The spectrum manager 11 comprises one BACC for coordinating the availability of all licensed bands. One exemplified frame format of the BACC is shown in FIG 5 including User ID, Avail. CH ID, Transmit Power, Channel Occupancy, and Release Code. The User ID denotes the ID of the PU whom BS broadcasts the message on control channel; Avail. CH ID denotes the available and free channels which can be used by SU including frequency and bandwidth (BW); Transmit Power denotes the allowable transmit power, i.e., restricted condition for SU to operate using CH ID constraints; Channel Occupancy denotes channel usage statistics, channel occupancy probability, user arrival probability in future, holding time; and Release Code denotes when PU wishes to come back again for transmission. FIG 4 illustrates the transmission of BACC to SU.

[0027] In one embodiment of the present invention, the BS further comprises a SSF module 12 embedded in the PHY layer; the operation of the SSF is detailed below in reference to FIG 7.

[0028] The present invention also provides a method for coordinated management of the coexistence of PUs and SUs in a wireless communication system. As shown in FIG 6, there is provided a block flowchart of the method of coordinated sensing and detection with BACC in accordance with one embodiment of the present invention.

[0029] The method 100 initializes the network entry process for PUs by communicating with BS to connect to selected network 110; then the BS recognizes all the PUs by sending control paging channel and receiving the responses from PUs within its range 120; and then the BS classifies active and idle PUs by monitoring their communication links and analyzing their utilization pattern 130. Then the BS decides whether the channel is idle 140; if the outcome is No, i.e., the channel is not idle, then the method goes back to step 120 to check the PUs again; if the outcome is Yes, i.e., the channel is idle, the BS advertises available channel for SUs by transmitting BACC to all SUs 150. Upon receiving the BACC, do the SUs check BACC within frequency band of interest to determine the instantaneous channel availability 160. Then the BS provides other important parameters such as channel bandwidth, allowable power, channel occupancy probability etc. 170. Then SU decides to utilize the available channel and transmit data to other SUs 180. Then SU decides whether a release code is received 190, if No, i.e., no release code is received, the method goes back to step 180; if Yes, i.e., a release code is received, SU detects BACC with a release code signal which specifies the time in which the channel must be vacated 200, and then SU stops operating in licensed band and start to use default sensing mechanism to detect spectral white 210; then the method comes to an end.

[0030] Referring now to FIG 7, there is provided a block flowchart of the process of the sensing and detection by the SSF in accordance with one embodiment of the present invention, where the SSF allows spectrum sharing among secondary users. The process of the sensing and detection by the SSF 700 comprises the following operations. On receiving BACC, CR performs additional sensing on free band information from the BACC 710; then CR communicates on the unlicensed band scanning results to mitigate the effect of shadowing or fading encountered during BACC reception 720; then CR decides whether the channel is below threshold 730; if No, i.e., the channel is not below threshold, the process goes back to step 710; if Yes, i.e., the channel is below threshold, CR negotiates on the usage of the free bands on the unlicensed band based on the application requirement by CR 740; then user with more bandwidth requirement gets more bandwidth of the free band, e.g., video 750. Then the process stops.

[0031 ] FIG 8 is a graph showing the simulation results (P_FA and P_M, where P_M = 1

- PD). The simulation parameters included: channel model = AWGN and Rayleigh fading; No. of PU =3; No. of SU =3; SNR = lOdB; M =5; W =1 ; Fs =2; N =Fs m; % sample points N=TW. Target P_D and P_FA: Based on 802.22, it is required to achieve 90% probability of detection (PD) and 1 0% probability of false alarm (PFA)- The fundamental tradeoff between P_M (probability of missed detection) and P_PA has different implications in the context of dynamic spectrum-sharing. A high PM would result in missing the presence of primary user with high probability which in turn increases interference to primary licensee; a high _PF_A would result in low spectrum utilization since false alarms increase number of missed opportunities (white spaces).

[0032] FIG. 9 illustrates simulation results of P_D in the factor of time, Ts. The dashed line represents the simulation results under lOdB while the solid line represents the simulation results under 8dB. The present method improves the sensing time i.e. the time required to detect spectrum hole, because the SUs scan only selective frequency instead of continuously scanning the entire frequency range, The SUs only search for BACC sent by PU base station or PUs themselves on specific frequency. In FIG. 9, the bolded line in the graph represents a desired result that can be achieved by the present invention. Such desired results can be achieved through PU cooperation whereby the required sensing time for SIJ is partially reduced because the SU does not need to scan through all the spectrum band as illustrated in FIG. 9.

[0033] While the present invention has been described with reference to particular embodiments, it will be understood that the embodiments are illustrative and that the invention scope is not so limited. Alternative embodiments of the present invention will become apparent to those having ordinary skill in the art to which the present invention pertains. Such alternate embodiments are considered to be encompassed within the scope of the present invention. Accordingly, the scope of the present invention is defined by the appended claims and is supported by the foregoing description.

Claims

What is claimed is: I . A system for sending and detecting wireless communication links involving the utilization of coordinated access control channel by PU, the system comprising

a spectrum manager operationally modifies MAC frame based on a role of Primary User (PU) to improve the accuracy of he white space detection and allocates an appropriate spectrum to Secondary User (SU);

spectrum sensing function (SSF) operatively sensing the spectrum for white space, whereby the SSF avoid sensing the whole spectrum of interest to reduce sensing time and overall complexity.

2. The system according to claim 1 , the modified MAC frame comprises a user ID of the PU BS who broadcast the message on control channel; a C'H ID for determining free channels allocable for SU; power information of the transmission that indicating allowable transmit power as one restricted condition for SU to operated using CH ID contrails; a channel occupancy; release code to grant channel access to PU when primary user wish to come back again for transmission.

3. The system according to claim 2, wherein the free channels includes frequency and/or bandwidth.

4. The system according to claim 2, wherein the channel occupancy includes channel usage statistics, channel occupancy probability, user arrival probability in future, and holding time.

5. A method of coordinating access among primary and secondary users in a wireless network, the method comprising:

initiating network entry process for PU, by communicating with the base station (BS) to connect with a selected wireless network;

recognizing all PU in the network by sending control paging channel;

receiving response from PU within the BS range;

classifying active and idle PU by monitoring communication links and analyze a utilization pattern;

checking available spectrum within cells by detecting the idle and busy channel; broadcasting available channels for SU by transmitting band access control channel (BACC) to all SU;

checking BACC within frequency band of interest for SU to determine instantaneous channels availability;

providing link condition parameters;

deciding to utilize the available channel and transmit data to other SU;

determining whether SU receives release code from PU;

detecting BACC with a release code signal specifying a time that the channel be vacated;

ceasing operation by the SU in PU frequency band and using default sensing mechanism to detect white space,

6. The method according to claim 5, the important link condition parameter includes channel bandwidth, allowable power, channel occupancy probability,

7. A method for sharing spectrum among secondary users, the method comprising: receiving BACC;

performing additional sensing by SU based on available band information obtained from BS;

communicating with nearby SU for available band

mitigating an effect of shadowing or fading encountered during BACC reception based on the sensing result;

checking and determining if the detected available channel power is below a prescribed threshold;

negotiating an usage of the available bands based on application requirements by SU, wherein user with more bandwidth requirement can be assigned with more bandwidth.