WO2010065280A2

WO2010065280A2 - Method for efficient reporting of channel quality information from user equipment to the network

Info

Publication number: WO2010065280A2
Application number: PCT/US2009/064675
Authority: WO
Inventors: Vinod Kumar Ramachandran; Richa Dham; Nitin Jain; Suresh Kalyanasundaram; Sayee Kalyanarama Sesha Kcv
Original assignee: Motorola, Inc.
Priority date: 2008-12-03
Filing date: 2009-11-17
Publication date: 2010-06-10
Also published as: WO2010065280A3

Abstract

A method for efficient reporting of Channel Quality Information (CQI) from User Equipment (UE) to a network. The method includes data communication between the UE (102) and eNodeB (104). To schedule the UE (102) the eNodeB (104) further requests for CQI of the top-m PRBs which is calculated at the eNodeB end, and the value of 'm' can be different for each UE. The UE (102) further reports the CQI of the determined number of PRBs. Thereafter, the eNodeB (104) selects the best channel based on the CQI received and schedules the UE (102) with the best PRB of the determined number of PRBs.

Description

CML04640

METHOD FOR EFFICIENT REPORTING OF CHANNEL QUALITY INFORMATION FROM USER EQUIPMENT TO THE NETWORK

FIELD OF THE INVENTION

[0001] The invention relates generally to a communication system based on Orthogonal Frequency Division Multiple Access (OFDMA), and particularly, it relates to a system and method for efficient reporting of Channel Quality Information (CQI) by reducing the number of CQI reports.

BACKGROUND OF THE INVENTION

[0002] In this age of rapid communication, there is an increasing demand for high speed data transfer in different types of services. Examples of such services include simple voice communication over phone, e-mail, General Packet Radio Service (GPRS), etc. At the same time, maintenance of Quality of Service (QoS), control of the data transfer rate, and reduction of error probability over these services are also required. With the advent of the Fourth Generation (4G) of the mobile communication network and a system that uses Orthogonal Frequency-Division Multiplexing (OFDM) modulation techniques, most of these demands are being met.

[0003] OFDMA is a multi-user variant of OFDM digital modulation scheme for access by one or more User Equipment (UE). Multiple access in OFDMA is attained by allotting subsets of subcarriers to the users of mobile phones or any other communication devices. These subsets of sub-carriers are known as Physical Resource Blocks (PRBs). The allocation of the PRBs requires Channel Quality

Information (CQI) of these PRBs from one or more UE that is served by a Base CML04640 Station (eNodeB). However, the reporting of CQI for all the PRBs by each UE results in excessive overhead in the uplink. The uplink is the transmission path followed from the UE to the eNodeB. The overhead in the uplink can also result in congestion in the network. Network congestion is a condition that arises when the number of active UE increases and is characterized by slow speed in data transfer and increased delay of pending calls.

[0004] Therefore, a scheme for reducing CQI reports is required in OFDMA- based networks, such as, Long Term Evolution (LTE), to avoid the uplink overhead. One of these schemes for reducing CQI reports is "Reporting average CQI" by grouping PRBs. For example, to get PRBs for communication, one or more User Equipment (UE) report average CQI for a set of PRBs. The number of PRBs in the set can be different for different UEs. The number of PRBs in a set is defined by eNodeB, so appropriately moving between different sets of PRBs to report average CQI of, for example, 2, 4, 8.... or 14 PRBs. The option of sending CQI reports for those PRB groups that have better CQI is more useful than reporting CQI for the plurality of Physical Resource Blocks (PRBs). In top-m CQI reporting, one or more UEs report the identity and the perceived CQI of its top-m PRBs. For example, in top-m CQI reporting scheme, the eNodeB requests one or more UEs to report CQI on their top-m PRBs, where the number 'm' is the same for all UEs and is determined by the eNodeB, based on a predefined condition. These CQI reporting schemes are not coupled with the network scheduler, so need for a CQI reporting scheme is there which is scheduler dependent. CML04640

[0005] The schemes mentioned above for reporting Channel Quality Information (CQI) from (UE) to the eNodeB, suffer from high overhead in the uplink due to excessive CQI reporting for many PRBs. The CQI reporting scheme must be efficient in terms of throughput, fairness among users, CQI overhead in the uplink and downlink, etc. The present invention provides a method by which CQI can be reported efficiently by reporting the CQI for only top-m PRBs, where the value of 'm' can be different for different UEs.

[0006] In light of the above, there is a need for an effective method for reducing the CQI reports and system for CQI reduction scheme that is coupled with the scheduler.

BRIEF DESCRIPTION OF THE FIGURES

[0007] The accompanying figures, wherein like reference numerals refer to identical or functionally similar elements throughout the separate views, and which together with the detailed description below, are incorporated in and form part of the specification, serve to further illustrate various embodiments and explain various principles and advantages, all in accordance with the present invention.

[0008] FIG. 1 illustrates an exemplary network where various embodiments of the present invention can be practiced, in accordance with the present invention;

[0009] FIG. 2 illustrates the distribution of UE that are served under the same eNodeB, in accordance with the present invention; CML04640 [0010] FIG. 3 illustrates an exemplary arrangement of multiple sub-carriers to form

PRBs in an OFDMA-enabled mobile network, in accordance with the present invention;

[0011] FIG. 4 illustrates the arrangement of a plurality of Physical Resource Blocks (PRBs) and UE in an ordered manner in an OFDMA-enabled mobile network, in accordance with the present invention;

[0012] FIG. 5 illustrates a block diagrams of a UE in communication with an eNodeB for channel quality indicator (CQI) reporting, in accordance with the present invention;

[0013] FIG. 6 illustrates a flow diagram for a method for reporting channel quality indicator (CQI), in accordance with the present invention; and

[0014] FIG. 7 and 8 illustrate another flow diagram for a method for reporting channel quality indicator (CQI), in accordance with the present invention.

[0015] Skilled professionals will appreciate that the elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn according to scale. In order to improve the understanding of various embodiments of the present invention, some elements in the figures are enlarged in dimension relative to other elements.

DETAILED DESCRIPTION

[0016] Various embodiments of the present invention describe a method for efficient reporting of channel quality information (CQI) from user equipment (UE) to CML04640 the eNodeB. The method includes the steps that take place between UE and eNodeB when a user wants to communicate with the eNodeB for any type of data service. A UE needs PRBs to be allocated before it can receive data from the eNodeB. The quality of service depends on the condition of the channel through which the communication takes place. Selection of the best channel from the available channels makes the communication more efficient and improves the quality of service. In accordance with various embodiments of the present invention, it should be observed that the present invention combines the method steps and system elements related to a method for efficient reporting of CQI from UE to the network.

[0017] For one embodiment, a method for reporting channel quality information (CQI) from one or more user equipment (UE) to a network is provided. The method includes receiving of data by a UE from the eNodeB in the network. In order to receive data, the eNodeB determines a pre-ordered list of UEs from the one or more UEs, based on a first set of parameters. Further the eNodeB determines the number of PRBs of the plurality of PRBs for each UE of the pre-ordered list of UEs useful for allocation while scheduling. The eNodeB requests CQI for the determined number of PRBs corresponding to each UE of the pre-ordered list of UE and finally schedules the UE with the best matched PRB in a priority order, based on the CQI received from a corresponding UE from the pre-ordered list of UE.

[0018] For another embodiment, a system for reporting channel quality information (CQI) from one or more user equipments (UEs) to a network is provided. CML04640

The UE is configured to report the computed CQI for the determined number of best PRBs. Further, the eNodeB is configured to calculate the determined number of PRBs, request CQI from each UE, and schedule the PRBs to the UE in order of priority.

[0019] FIG. 1 illustrates a network 100, where various embodiments of the present invention can be practiced, in accordance with the present invention. The network 100 includes a User Equipment (UE) 102 and base station (eNodeB) 104. The network 100 is an orthogonal frequency-division multiple access (OFDMA)- enabled network. Examples of the network 100 include, but are not limited to Fourth Generation (4G) standards networks such as LTE, WiMAX, and Ultra Mobile Broadband, and the like. Examples of UE can include, but are not limited to, a mobile phone, a pager, a personal digital assistant (PDA), a fixed line phone, and other communication devices. The communication between different users is initiated based on the available data in the buffer of eNodeB 104 and other pre-defined parameters, the eNodeB 104 will allocate PRBs to the UE 102 automatically. The allocation is based on the reporting of CQI from the UE. In OFDMA systems, there are multiple sub-carriers which are grouped into one or more Physical Resource Blocks (PRBs). A sub-carrier is a signal carrier that is used to carry data over a communication channel. Each PRB contains a fixed number of sub-carriers. The eNodeB 104 in the OFDMA-enabled mobile network 100 assigns a subset of the multiple sub-carriers to the UE 102 to enable the communication. In order to identify the subset of the multiple sub-carriers best suited for the UE 102, the eNodeB 104 CML04640 makes a request for Channel Quality Information (CQI) from the UE 102 and other

UEs that request for communication. Based on the CQI received from the UE 102 and other UEs, the availability of the one or more PRBs and the number of PRBs required by the UE 102, the eNodeB 104 identifies and allocates PRBs to the UE to enable communication. The allocation of PRBs to the UE 102 has been described in detail in conjunction with FIG. 4.

[0020] FIG. 2 illustrates an exemplary distribution of UEs in an OFDMA-enabled mobile network 100, in accordance with an embodiment of the present invention. The network 100 includes the eNodeB 104 in the cell 202, a group of eNodeBs in the cell, the UE 102 and other UEs of the cell 202. The eNodeB 104 and the group of eNodeBs in the cell 202 provide communication to the UE 102 and the other UE in the cells 202 by operating in a cell arrangement 200, as shown in FIG. 2. Each cell of the cell arrangement 200 indicates the region where a particular base station (eNodeB) can provide communication to UEs in that cell. Each cell of the cell arrangement 200 indicates a geographical region where a base station corresponding to that cell provides communication. For example, the eNodeB 104 provides communication to UE 102, when the UE 102 is present in the cell 202. Similarly, when the UE 102 is present in the cell 206, the eNodeB 204 provides communication to the UE 102. Typically, each cell of the cell arrangement 200 is arranged in the form of hexagonal cells. This means that in the field of telecommunication networks the eNodeB 104 will be a base station set up by a telecommunication service provider of the UE 102 which can be a mobile phone. The cell arrangement 200 ensures that the call through CML04640 the UE 102 does not disconnect when a user of the UE 102 moves during the call from the cell 202 to a cell 206.

[0021] An eNodeB can serve the UE 102 and other UEs of the cell 202 based on the capacity of the network. This means that the eNodeB 104 can serve UEs depending on the number of PRBs available with it and the number of PRBs required by each UE. Therefore, if there are large numbers of UE in the cell 202, then it becomes cumbersome to serve all the UE by the eNodeB 104. Further, the communication is said to be efficient if one or more UEs are allocated PRBs with good channel condition, the probability of error is low and the allocation or scheduling of channel to the UE is fast. In order to provide an efficient communication, the eNodeB 104 needs to schedule the best suited PRB from the plurality of PRBs available in the network 100 in the cell 202. In accordance with the present invention, to identify the best suited PRB, the eNodeB 104 requests Channel Quality Information (CQI) from the UE 102 and the other UEs present in the cell 202. Based on the CQI reports from the UE 102 and the other UEs of the cell 202, the one or more PRBs are allocated to the UE 102 and the other UEs of the cell 202 such that each pair of UE and PRBs can provide the best possible communication to the corresponding UE. Further, if the CQI reporting is done relatively fast, it improves the OFDMA robustness to fast fading and narrow-band channel interference. It will be apparent to those skilled in the art that the details of the invention, as described in conjunction with the eNodeB 104 and the cell 202 can be applicable to the group of eNodeBs 206, the cell arrangement 200, and the network 100. Hereinafter, the other CML04640 UEs in the cell 202 and the network 100 will be referred to as UEs present in the cell

202 of the eNodeB 104 for the sake of clarity.

[0022] FIG. 3 illustrates an exemplary arrangement of multiple sub-carriers 300 to form a PRB 302 in the OFDMA-enabled mobile network 100. These set of sub- carriers are known as Physical Resource Block (PRB). Each PRB in the network has a fixed number of sub-carriers. The eNodeB 104 in the OFDMA-enabled mobile network 100 assigns a subset of the sub-carriers 300 to individual UEs. For example, the eNodeB 104 can assign the PRB 302 to the UE 102 when the PRB 302 is identified as the best suited PRB for the UE 102. In some cases, based on the requirements of the UE 102, the eNodeB 104 can assign more than one PRB to the UE 102. OFDMA is considered to be suitable for broadband wireless networks (e.g., LTE, and IEEE 802.16) because of its advantages that include scalability and ability to take advantage of channel frequency selectivity. The scalability of a mobile network indicates its ability to handle the increasing amount of requests for communicating in an efficient manner. For example, it refers to the capability of the eNodeB 104 to increase total throughput when the number of UEs (102, 402, 404 ,

410) increases in the network. The method for allocation of the suited PRB to the UE 102 has been described in detail in conjunction with FIG. 4

[0023] FIG. 4 illustrates an arrangement of the UE 102, the other UEs in the cell 206 and plurality of PRBs (412, 414 422) and the eNodeB 104 in an OFDMA- enabled mobile network 100 for efficient CQI reporting. The other UEs in the cell CML04640 206 include a number of UEs (402, 404 , 410), along with the UE 102 that require to communicate with some application server, some other UE or with each other.

[0024] To explain the invention, let us consider that Jim is a user of the UE 102 and is performing active data communication with the eNodeB. At the same time, it is possible that users of at least one UE of the other cell 206 are also involved in data communication. This is possible because in telecommunication networks, the number of users with mobile phones (UE) is very high. Before transmitting data to Jim, the eNodeB 104 can arrange the UEs in a pre-ordered list based on preferred order in which UE will be allocated and scheduled. Therefore, the UE (102, 402, 404 , 410) are arranged in a pre-ordered list by the eNodeB 104. The pre-ordered list is based on a first set of parameters. The first set of parameters can include Quality of Service (QoS) metrics, such as, guaranteed bit rate, delay target, packet loss target, of the different UEs; filtered average of the past reported CQI for each UE over all PRBs, that is in the given example is plurality of PRBs (412, 414 422); and throughput received so far for each UE.

[0025] The eNodeB 104 first determines the number of PRBs (412, 414 422) that it needs to allocate to the different UEs in the pre-ordered list of UEs, based on their QoS parameters, amount of data in the buffer, and fairness. The eNodeB 104 then considers the location of the UEs in this pre-ordered list and the number of PRBs needed by that UE and all the UEs ahead of it in the pre-ordered list to determine the number of CQI reports it will request of each user. In one simple embodiment, this CML04640 number is the sum of the number of PRBs (412, 414 422) needed by the given UE and all the UEs that are ahead of it in the pre -ordered list. Assuming that this is the number of CQI reports made by each UE, the eNodeB 104 can check the availability of bandwidth for receiving the CQI. To make sure that the bandwidth needed for CQI reports is below the threshold allowed for CQI reports, the eNodeB 104 determines the probability of allocation of each PRB of the determined number of PRBs to the corresponding UE in the pre-ordered list of UEs. For the present example, the eNodeB 104 determines the probability of allocation of three best PRBs (412, 414, and 416) for the UE 102. The probability of allocation is determined based on the fact that the eNodeB 104 knows the order in which it will allocate PRBs to different UEs, and the PRB requirements of different UEs. Therefore, it is possible to analytically estimate the probabilities with which each UE gets allocated the different PRBs. In other words, for the UE 102, we can determine the probability with which it will get allocated to its most preferred PRB of the determined set of PRBs (412, 414, and 416), the probability with which it will get its next preferred PRB, and so on.

[0026] Let us consider a case in which there are 'n' PRBs (plurality of PRBs) and 'n' UEs, i.e., the number of PRBs is equal to the number of UEs in a network such that each UE needs an allocation of at least one PRB. The eNodeB 104 determines the number of PRBs for which the CQI is required from the one or more UEs present in the network. Suppose the number of PRBs for each UE in the network is 'r'. Therefore, the eNodeB 104 can find the probability with which the k-th UE is allocated with m-th best PRB of the determined set of 'r' best PRBs, considering that CML04640 each UE among the 'n' number of UE is allocated with the corresponding best matched PRB of the plurality of PRBs, if the best matched PRB is not already allocated to other UEs ahead of the given UE in the list. Therefore, the k-th UE gets its best matched PRB if its best matched PRB does not coincide with the allocations made to the (k-1) UEs ahead of the k-th UE in the pre-ordered list. Therefore, the probability of allocation of the best matched PRB for the k-th UE will be:

(n-k+l)/n

Similarly, the k-th UE gets its second best PRB of the 'r' PRBs, if the best PRB coincides with any of the allocations made to the (k-1) UEs ahead of the k-th UE in the pre-ordered list, and the second best PRB does not coincide with the allocations made to the (k-1) UEs ahead of the k-th UE in the pre-ordered list. The probability of allocation of the second best PRB for the k-th UE will be:

(k -l/n)*(n-k+l/ (n-l))

Similarly, the probability of allocation of the m-th best matched PRB where m<=k to the k-th UE will be:

(k-l/n)*(k-2/n-l)*(k-3/n-2)... *(k-m+l/n-m+2)*(n-k+l/n-m+l)

[0027] By observing the probability distribution mentioned above, it can be concluded that the probabilities are monotonically decreasing with respect to m, i.e., the probability with which a UE is allocated to a lower ranked PRB is smaller. Therefore, if the k-th UE is made aware of its position in the pre-ordered list at the eNodeB, the k-th UE need not report CQI for more than the top 'k' PRBs. In this CML04640 way, the number of CQI reports reported by a UE can be reduced which will subsequently reduce the overhead in the uplink and congestion in the network.

[0028] In one embodiment of the present invention, the product of the expected throughput at the determined Signal to Noise Ratio (SNR) of each PRB (412,

414 422) with the corresponding probability of allocation is also used for ranking the plurality of PRBs in order to arrange it in a preferred order. As many entries from this ordered list of (UE, PRB) pair are included as will fit within the uplink bandwidth set aside for CQI reports. A given UE in the ordered list is requested to report as many reports as the number of entries for that UE that made it to the above shortlisted (UE, PRB) pair indices. In another embodiment of the present invention, the plurality of PRBs (412, 414 422) can be ranked on the basis of probability of allocation, a SNR, and many other related parameters.

[0029] FIG. 5 illustrates a block diagram of the UE 102 in communication with the eNodeB 104 for CQI reporting. To describe the invention, references will be made to FIGs. 1, 2, 3 and 4, although it will be apparent to those skilled in the art that the present invention can be applicable in any other embodiment of the present invention. The eNodeB 104 includes a transmitter 502, a receiver 504, and a scheduler 506. In some cases, the scheduler 506 can include an estimator 508. The UE 102 includes a CQI calculator 510. In addition, there can be many other system elements of the eNodeB 104 and the UE 102 that are required for their proper functioning. CML04640 [0030] As described in conjunction with FIG. 4, the eNodeB 104 arranges the UE

102 and other UE (402, 404 , 410) in a pre-ordered list, based on the first set of parameters. The one or more UE in the pre-ordered list is arranged in a preferred order of allocation. The scheduler 506 in the eNodeB 104 requires CQI for the best PRBs corresponding to each UE in the pre-ordered list to allocate the best PRB corresponding to each UE. The estimator 508 determines the number of PRBs corresponding to the UE 102 in the pre-ordered list of UEs for which CQI is required from the UE 102.

[0031] The determined number of PRBs is preferable for allocation with the UE. The transmitter 502 communicates the determined number of PRBs to the UE 102 and requests for CQI reports corresponding to the determined number of best PRBs. On receiving the request for CQI reports, the UE 102 calculates the CQI for all PRBs by using the CQI calculator 510 and reports the CQI of the determined number of best PRBs.

[0032] The CQI calculator 510 calculates the CQI of the determined set of best PRBs and transmits the CQI reports to the eNodeB 104. Thereafter, the scheduler 506 allocates PRBs to UE based on the position of the UE in the pre-ordered list.

[0033] FIG. 6 illustrates a flow diagram for a method for reporting channel quality information (CQI), in accordance with the present invention. To describe the invention, references will be made to FIGs. 1, 2, 3, 4 and 5, although it will be apparent to those skilled in the art that the method will be applicable to any other CML04640 embodiment of the present invention. At step 602, the method initiates. The UE 102 in the network 100 has some data buffered in the eNodeB 104 meant to be transmitted to UE 102. At the same time, the other UE (402, 404 , 410) may also have some data buffered in the eNodeB 104. At step 604, the eNodeB 104 arranges one or more

UEs (the UE 102 and other UEs (402, 404 , 410)) in a pre-ordered list, based on a first set of parameters. The first set of parameters can include Quality of Service (QoS), filtered average of the past CQI reports over plurality of PRBs of each UE of the one or more UEs (the UE 102 and other UEs (402, 404 , 410)), throughput received so far for each UE of the one or more UEs, and many other related parameters. In an embodiment of the present invention, the scheduler 506 arranges the one or more UEs (the UE 102 and other UEs (402, 404 , 410)), in the pre- ordered list. At step 606, the eNodeB 104 determines the number of PRBs for each UE of the pre-ordered list. It will be apparent to those skilled in the art that the determined number of PRBs for each UE in the pre-ordered list need not be the same as the number of PRBs that will actually be allocated to the corresponding UE at the time of communication. In one embodiment of the present invention, the estimator 508 determines the number of PRBs corresponding to the UE 102 in the pre-ordered list of UE for which CQI is required from the UE 102.

[0034] At step 608, the eNodeB 104 transmits the determined number of PRBs to request for CQI reports from the corresponding UE in the pre-ordered list of UEs. The number of CQI reports requested will be the same as the determined number of PRBs. On receiving the request for CQI reports, the UE 102 and the other UEs (402, CML04640 404,..., 410) calculate the CQI for the determined number of best PRBs. In some cases, the UE 102 can calculate CQI by using the CQI calculator 510. Thereafter, the UE 102 transmits the CQI reports to the eNodeB 104. At step 610, the eNodeB 104 schedules the plurality of UEs in a previously arranged priority order based on the

CQI reports received from one or more UEs (the UE 102 and other UEs (402, 404 ,

410)). The method terminates at step 612.

[0035] FIG. 7 and 8 illustrate another flow diagram for a method for reporting CQI from the UE 102 to the eNodeB 104, in accordance with the present invention. To describe the invention, references will be made to FIGs. 1, 2, 3, 4 and 5, although it will be apparent to those skilled in the art that the method will be applicable to any other embodiment of the present invention. For the sake of clarity, the method for reporting CQI is described for reporting of CQI from the UE 102, and it will be apparent that the method is applicable to any number of UEs. In some cases, the present invention is based on the top-m CQI reporting scheme. Furthermore, the invention need not be limited to the order in which the steps are listed in the method.

[0036] At step 702, the method initiates. At step 704, the eNodeB 104 arranges one or more UEs (102 and other UEs (402, 404,..., 410)) in a pre-ordered list, based on first set of parameters. The first set of parameter can include Quality of Service (QoS), filtered average of the past CQI over the plurality of PRBs of each UE of the one or more UEs (102 and other UEs (402, 404, ..., 410)), and the throughput received so far from each UE of the one or more UEs (102 and other UEs (402, 404, ..., 410)) and many other related parameters. It will be apparent to those skilled in the art that CML04640 the each UE of the one or more UEs (102 and other UEs (402, 404, ..., 410)) arranged in the pre-ordered list are part of the cell 202, i.e., in the vicinity of the eNodeB 104. At step 706, the eNodeB 104 determines a number of PRBs for each UE of the pre- ordered list. Therefore, the eNodeB 104 determines a number of PRBs for the UE 102. The eNodeB 104 first determines the number of PRBs that it needs to allocate to the different UEs in the pre-ordered list of UEs, based on their QoS parameters, amount of data in the buffer, and fairness. The eNodeB 104 then considers the location of the UEs in this pre-ordered list and the number of PRBs needed by that UE and all the UEs ahead of it in the pre-ordered list to determine the number of CQI reports it will request of each user. In one simple embodiment, this number is the sum of the number of PRBs needed by the given UE and all the UEs that are ahead of it in the pre-ordered list. As described in conjunction with FIG. 1, the UE 102 can be any communication device, for example, a cell phone, a pager, a smart phone, a communicator, etc., Further, the UE 102 and the eNodeB 104 can be part of a telecommunications network, wireless network, wire line network, Fourth Generation (4G) standards networks, and the like using OFDMA.

[0037] The determined number of PRBs is communicated to the corresponding UE 102 and other UEs (402, 404, ..., 410) of the pre-ordered list in order to report the CQI on the determined number of best PRBs. Each UE can have a different determined number of PRBs. It should be apparent that the number of PRBs in the determined number of PRBs corresponding to the UE 102 need not be the same as the number of PRBs that will actually get allocated to the UE 102 while scheduling. At CML04640 step 708, the eNodeB 104 checks the availability of uplink bandwidth or the bandwidth required to accommodate in the communication network 100 over which CQI will be reported. Examples of the constraints on bandwidth can include, but are not limited to, CQI feedback, overload in uplink/downlink, physical constraint, etc. The eNodeB 104 can be capable of finding any constraints in the communication network 100.

[0038] At step 708, when the eNodeB 104 on checking the availability of bandwidth finds that bandwidth is not available, the eNodeB 104 is required to reduce the number of CQI reports requested from one or more UEs (102 and other UEs (402, 404 , 410)) at step 710 in order to avoid overhead in the network 100.

[0039] The eNodeB 104 can select an appropriate method for reducing the number of CQI reports requested from each UE of the one or more UE (102 and other UE (402, 404, ..., 410)). There can be different method for reducing the number of CQI reports requested from UE. One of the methods to reduce CQI reports includes selecting preferred (UE, PRB) pairs from their corresponding ranked list such that the number of requested CQI reports is such that they can be reported within the CQI bandwidth constraints. This means that instead of reporting CQI for the originally determined number of PRBs, the UE in the pre-ordered list of the one or more UEs (102 and other UEs (402, 404, ..., 410)) can report the CQI for only fewer PRBs, i.e., the top few PRBs in the preferred order of the determined number of PRBs. Such a CML04640 method will reduce the number of CQI reports requested from the one or more UEs

(102 and other UEs (402,404, ..., 410)).

[0040] Another method for reducing the number of CQI reports is for the eNodeB 104 to request CQI from one or more UEs (102 and other UEs (402, 404, ..., 410)) in the pre-ordered list of UEs for a first number of PRBs from the determined number of PRBs. The first number of PRBs contains PRBs whose probability of allocation is greater than a predefined value. The pre-defined value is dependent on the eNodeB 104 and can vary from an eNodeB to another eNodeB. The method further includes the eNodeB 104 requesting a set of UEs in the pre-ordered list of UE to report an average CQI on a second set of PRBs.

[0041] There can be one or more UEs (102 and other UEs (402, 404, ..., 410)) and a plurality of PRBs (412, 414, ..., 422) in a communication network 100. The PRB is allocated to at least one UE in order to communicate with a network application server or other UEs in the network 100.

[0042] In accordance with another embodiment of the present invention, sometimes the UE 102 requires more than one PRB from the plurality of PRBs (412, 414, ..., 422) for communication. This requirement of PRB allocation can result from the condition of large data transfer, requirement of high data rate, etc. Therefore, if one or more UEs (102 and other UEs (402, 404, ..., 410)) of the pre-ordered list of UE requires allocation of two or more PRBs from the plurality of PRBs (412, 414, ..., CML04640 422), then the determined number of PRBs is increased by the network 100 for the UE to which CQI is requested.

[0043] Further at step 712, the eNodeB 104 determines two parameters related to the plurality of PRBs. These two parameters are probability of allocation of each PRB of the determined number of PRBs to the corresponding UE of the pre -ordered list of UE and mean signal-to-noise ratio (SNR) of each PRB of the determined number of PRBs. These two parameters can be used to rank the PRBs in a preferred order at step 804. The process of calculating the probability of allocation of each PRB of the determined set of PRBs to the corresponding UE and SNR has been described in conjunction with FIG. 4. In addition, in some cases, the product of the expected throughput at the determined SNR of each PRB with the corresponding probability of allocation can also be used for ranking the PRBs in the preferred order.

[0044] At step 802, the eNodeB 104 calculates the product of the expected throughput at the determined SNR of each PRB with the corresponding probability of allocation of each PRB of the determined set of PRBs to the corresponding UE. The process of calculating probability of allocation of each PRB of the determined set of PRBs to the corresponding UE has been described in conjunction with FIG. 4.

[0045] At step 804, the plurality of PRBs (412, 414, ..., 422) is ranked on the basis of the two parameters that are probability of allocation of each PRB of the determined CML04640 set of PRBs to the corresponding UE of the pre-ordered list of UE. The plurality of

PRBs (412, 414, ..., 422) is then arranged in decreasing order of its rank in order to determine the set of PRBs for which CQI is requested. The arrangement of the PRBs in decreasing order is based on the product value of the expected throughput at the SNR of each PRB with the corresponding probability of allocation of PRB, as calculated at step 802.

[0046] Further, when the bandwidth for CQI reporting is available as determined at step 708, the eNodeB 104 request for CQI as described at step 806.

[0047] At step 806, the eNodeB 104 requests CQI reports for the determined number of PRBs based on the ranking of the one or more UEs (102 and other UEs (402, 404, ..., 410)) from the corresponding UE in the pre-ordered list.

[0048] At step 808, each UE of the one or more UEs (102 and other UEs (402, 404, ..., 410)) is scheduled with its respective best matched PRB of the respective determined set of PRBs. In an embodiment of the present invention, the scheduler 506 in the eNodeB 104 schedules the UE 102 to its corresponding best matched PRB among the identified top-m PRBs (412, 414, 416). The scheduler in the eNodeB 104 is the system element which is involved in the whole process of scheduling. Therefore, the scheduler 506 now has the information about the top-m PRBs for the CML04640 corresponding UE in the pre-ordered list of UE. The top-m PRBs are calculated on the basis of the CQI provided by the UE in the pre-ordered list of UEs.

[0049] In accordance with an embodiment with the present invention, the one or more UEs are arranged in the pre-ordered list as 102, 402, 404, ..., 410. The determined set of PRBs for the UE 102 and 402 are arranged in the preferred order as 412, 414, 416 and 416, 418, 420, respectively. The scheduling starts with the first UE 102 in the pre-ordered list as the first UE 102 in the list that has the highest priority. The priority is given to the UE that are arranged in a preferred order based on CQI reports received from one or more UEs (the UE 102 and other UEs (402, 404 ,

410)). The first UE 102 in the pre-ordered list is scheduled with the best PRB 412 of the determined set of PRBs (412, 414, 416). The UE 102 having the highest priority can require more than one PRB to be allocated, then the next best PRB 414 gets allocated to it and this process takes place until the scheduling of the UE is done with the required number of PRBs. Once the scheduling of the first UE 102 in the list is completed, the second UE 402 in the pre-ordered list gets scheduled. The scheduler 506 in the eNodeB 104 schedules the best PRB from the determined set PRBs for the second UE 402, if it is not already allocated to the first UE 102. Further, if it is already allocated it to the first UE 102, it will then schedule the second UE 402 on its next best PRB from the determined set of PRBs. The eNodeB 104 will continue doing this scheduling for all UEs in the pre-ordered list of UEs. CML04640 [0050] As shown in step 704, the scheduler makes an arrangement of the UE in a pre-ordered list based on a first set of parameters. The arrangement of UEs is meant to be used as a basis for scheduling in the next sub-frame; therefore, the first UE 102 in the pre-ordered list is the one that gets top priority in the next sub-frame. The CQI reporting scheme is scheduler dependent.

[0051] FIG. 9 illustrates a graph for the probability of UE being allocated to the reported preferences, in accordance with the present invention. The scale on the Y- axis of the graph shows the probability that the n-th preference will be allocated to the UE in the pre-ordered list, whereas the scale on the X-axis of the graph shows the preference of the PRBs based on the CQI received. The eNodeB 104 will schedule the first UE in the pre-ordered list to its best PRB. It will then schedule the second UE in the pre-ordered list to its best PRB if that was not already allocated to the first UE in the pre-ordered list. If it has already been allocated to the first UE, it will schedule the second UE on its next best PRB. Likewise the graph will take a look as shown in FIG. 9.

[0052] The graph shown in FIG. 9 shows that the probability of allocation of the first UE in the pre-ordered list to its best PRB i.e., based on the reported CQI is 1 and likewise the probability of allocation of the other UE in the pre-ordered list to its best preference keeps on decreasing, which can be clearly seen in the graph. The probabilities are monotonically decreasing, i.e., the probability with which a user gets his lower choice is smaller. CML04640

[0053] FIG. 10 illustrates a graph for comparison between the throughput of the top-m scheme and the throughput of the scheme described in the present invention. The throughputs in both the schemes are against the probability that the user throughput is smaller than the corresponding value on the x-axis, i.e., Cumulative Distribution Function (CDF). The SNR (Signal-to-noise ratio) is exponentially distributed with mean dependent on the distance of the UE from eNodeB. In some cases, the detailed analysis of the graph shown in FIG. 10 yields a 6.83% improvement in system throughput over the top-m scheme which proves that the scheme described in the present invention is more efficient in terms of throughput in comparison to the top-m scheme.

Claims

CML04640 What is claimed is:

1. A method for reporting Channel Quality Information (CQI) from one or more User Equipments (UEs) to a network, the network comprising at least one base station (eNodeB) operating in an orthogonal frequency division multiple access (OFDMA) system, the OFDMA system comprising a plurality of Physical Resource Blocks (PRBs), each PRB of the plurality of PRBs comprising a set of contiguous sub- carriers, the method at the eNodeB comprising the steps of: determining a pre-ordered list of UE from the one or more UE based on a first set of parameters; determining number of PRBs of the plurality of PRBs for each UE of the pre- ordered list of UEs useful for allocation while scheduling; requesting CQI for the determined number of PRBs corresponding to each UE of the pre-ordered list of UE; and scheduling the at least one PRB from the determined number of PRBs in a priority order based on the CQI received from a corresponding UE from the pre-ordered list of UEs.

CML04640

2. The method as recited in claim 1, wherein one or more UEs in the pre -ordered list of UEs is ordered in preferred order of scheduling, wherein the preferred order of scheduling is based on the first set of parameters.

3. The method as recited in claim 1, wherein the first set of parameters comprises Quality of Service (QoS), filtered average of the past CQI over all PRBs of each UE of the one or more UEs, and throughput received so far from each UE of the one or more UEs.

4. The method as recited in claim 1, wherein the step of determining the number of PRBs further comprises the steps of: checking bandwidth available for receiving the CQI; determining probability of allocation of each PRB of the determined number of PRBs to the corresponding UE of the pre-ordered list of UEs; determining mean Signal-to-Noise Ratio (SNR) of each PRB of the determined number of PRBs; calculating product of expected throughput at the determined SNR of each

PRB with the corresponding probability of allocation; and ranking each PRB based on pre-defined ranking parameters, wherein the ranking determines the preference of PRB for finding the determined number of PRBs.

5. The method as recited in claim 4, wherein the pre-defined ranking parameters comprises the product of expected throughput at the determined SNR with the corresponding probability of allocation, probability of allocation, and SNR.

6. The method as recited in claim 4 further comprising checking constraints on bandwidth for receiving the CQI. CML04640

7. The method as recited in claim 6, wherein the constraints result in reducing number of CQI reports requested from each UE of the pre-ordered list of UEs based on the constraints on the bandwidth for receiving the CQI, and wherein reducing the number of CQI reports comprises: selecting preferred (UE, PRB) pairs from the corresponding ranked list such that the number of requested CQI reports is within the CQI bandwidth constraint. requesting CQI from each UE of the pre-ordered list of UEs for a set of PRBs from the determined number of PRBs, wherein each PRB of the set of PRBs has probability of allocation greater than a pre-defined value; and requesting a set of UEs of the pre-ordered list of UEs to transmit an average CQI on a subset of PRBs.

8. The method as recited in claim 4, wherein the product of expected throughput at the SNR of each PRB with the corresponding probability of allocation of PRB is arranged in decreasing order for determining the number of PRBs for which the CQI is requested.

9. The method as recited in claim 4, wherein the step of scheduling the determined number of PRBs comprises scheduling each UE of the pre-ordered list of UEs with at least one PRB of the corresponding determined number of PRBs based on the CQI received.

CML04640

10. A system for reporting Channel Quality Information (CQI) from one or more User Equipment (UEs) in an orthogonal frequency division multiple access (OFDMA) enabled network, the OFDMA enabled network comprising a plurality of Physical Resource Blocks (PRBs), each PRB of the plurality of PRBs comprising a set of contiguous sub-carriers, the system comprising: a base station (eNodeB) configured for determining number of PRBs for which CQI is requested, wherein the eNodeB further comprising a scheduler; and a UE configured for transmitting the CQI of the determined number of PRBs.