CAVALCANTE ANDRE MENDES (BR)
MARQUEZINI MARIA VALÉRIA (BR)
SOUZA DAYNARA DIAS (BR)
BORGES GILVAN SOARES (BR)
RODRIGUES ROBERTO MENEZES (BR)
COSTA JOÃO C WEYL ALBUQERQUE
VALCARENGHI LUCA (BR)
ALMEIDA IGOR (BR)
US20220302994A1 | 2022-09-22 | |||
US20210344389A1 | 2021-11-04 | |||
KR20210020475A | 2021-02-24 |
HIEN NGO ET AL.: "On the Total Energy Efficiency of Cell-Free Massive MIMO", IEEE TRANSACTIONS ON GREEN COMMUNICATIONS AND NETWORKING, March 2018 (2018-03-01)
EMIL BJORNSON ET AL.: "Scalable Cell-Free Massive MIMO Systems", IEEE TRANSACTIONS ON COMMUNICATIONS, July 2020 (2020-07-01)
VIDA RANJBAR ET AL.: "Cell-free mMIMO Support in the O-RAN Architecture: A PHY Layer Perspective for 5G and Beyond Networks", IEEE COMMUNICATIONS STANDARDS MAGAZINE, April 2022 (2022-04-01)
Claims 1. A method (300) in a first processing apparatus (102, 104, 106, 108, 402, 1000) of processing a connection request from a first User Equipment, UE (202, 204, 206, 408), wherein the first processing apparatus processes signals for one or more first Access Points, APs (110, 208, 210, 212, 214, 216, 404), the method comprising: receiving (302) a connection request (410) for the first UE to connect to one of the one or more first APs; determining (304) whether an identifier of the first UE is associated with the first processing apparatus and/or one of the one or more first APs; if the identifier of the first UE is not associated with the first processing apparatus and/or one of the one or more first APs, determining (306) whether a number of further UEs served by the one or more first APs is below a threshold number, wherein the further UEs each comprise a UE that has an identifier that is not associated with the first processing apparatus and/or one of the one or more first APs; and if the number of further UEs is below the threshold number, serving (308) the first UE. 2. The method of claim 1, wherein determining (304) whether an identifier of the first UE (202, 204, 206, 408)is associated with the first processing apparatus (102, 104, 106, 108, 402, 1000) and/or one of the one or more first APs (110, 208, 210, 212, 214, 216, 404) comprises determining whether the identifier of the first UE was assigned by and/or sent to the first UE by the first processing apparatus and/or one of the one or more first APs. 3. The method of claim 2, comprising determining that the identifier of the first UE (202, 204, 206, 408) was assigned by and/or sent to the first UE by the first processing apparatus (102, 104, 106, 108, 402, 1000) and/or one of the one or more first APs (110, 208, 210, 212, 214, 216, 404), and wherein the method comprises, before determining whether an identifier of the first UE is associated with the first processing apparatus and/or one of the one or more first APs, assigning and/or sending the identifier to the first UE. 4. The method of any of claims 1 to 3, wherein the method comprises, if the number of further UEs is equal to or above the threshold number: determining, based on a channel quality of a channel between the one or more first APs (110, 208, 210, 212, 214, 216, 404) and each of a plurality of UEs that comprise the first UE (202, 204, 206, 408) and UEs served by the one or more APs, a UE with a lowest channel quality of the plurality of UEs; if the first UE is not the UE with the lowest channel quality, dropping a connection with the UE with the lowest channel quality, and serving the first UE. 5. The method of claim 4, wherein, if the first UE (202, 204, 206, 408) is the UE with the lowest channel quality, rejecting the connection request from the first UE. 6. The method of claim 5, comprising preventing the first UE (202, 204, 206, 408) from connecting to any of the one of the one or more first APs (110, 208, 210, 212, 214, 216, 404) after rejecting the connection request from the first UE. 7. The method of claim 6, wherein preventing the first UE (202, 204, 206, 408) from connecting to any of the one of the one or more first APs (110, 208, 210, 212, 214, 216, 404) comprises rejecting subsequent requests from the first UE to join any of the one or more first APs. 8. The method of any of claims 1 to 7, wherein determining (304) whether an identifier of the first UE (202, 204, 206, 408) is associated with the first processing apparatus (102, 104, 106, 108, 402, 1000) and/or one of the one or more first APs (110, 208, 210, 212, 214, 216, 404) comprises determining whether the first UE will be served by one or more further APs, wherein one or more further processing apparatus processes signals for the one or more further APs. 9. The method of claim 8, wherein the first processing apparatus (102, 104, 106, 108, 402, 1000) is connected to the one or more further processing apparatus via backhaul. 10. The method of any of claims 1 to 9, wherein the one or more first APs (110, 208, 210, 212, 214, 216, 404) are connected to the first processing apparatus (102, 104, 106, 108, 402, 1000) via fronthaul. 11. The method of any of claims 1 to 10, wherein the further UEs comprise UEs that are also served by one or more further APs, wherein one or more further processing apparatus processes signals for the one or more further APs. 12. The method of any of claims 1 to 11, wherein the signals for the one or more first APs (110, 208, 210, 212, 214, 216, 404) comprise signals received by the one or more first APs and/or signals transmitted by the one or more first APs. 13. The method of any of claims 1 to 12, wherein the connection request (410) identifies the identifier of the first UE (202, 204, 206, 408). 14. A method (500) in a system (400), wherein the system comprises a first processing apparatus (102, 104, 106, 108, 402, 1000), one or more first Access Points, APs (110, 208, 210, 212, 214, 216, 404), and a first User Equipment, UE (202, 204, 206, 408), wherein the first processing apparatus processes signals for one or more first APs, the method comprising: sending (502), by the first UE, a connection request to connect to one of the one or more first APs; determining (504), by the first processing apparatus, whether an identifier of the first UE is associated with the first processing apparatus and/or one of the one or more first APs; if the identifier of the first UE is not associated with the first processing apparatus and/or one of the one or more first APs, determining (506), by the first processing apparatus, whether a number of further UEs served by the one or more first APs is below a threshold number, wherein the further UEs each comprise a UE that has an identifier that is not associated with the first processing apparatus and/or one of the one or more first APs; and if the number of further UEs is below the threshold number, serving (508), by the first processing apparatus, the first UE. 15. The method of claim 14, wherein determining (504) whether an identifier of the first UE (202, 204, 206, 408) is associated with the first processing apparatus (102, 104, 106, 108, 402, 1000) and/or one of the one or more first APs (110, 208, 210, 212, 214, 216, 404) comprises determining whether the identifier of the first UE was assigned by and/or sent to the first UE by the first processing apparatus and/or one of the one or more first APs. 16. The method of claim 15, comprising determining, by the first processing apparatus (102, 104, 106, 108, 402, 1000), that the identifier of the first UE (202, 204, 206, 408) was assigned by and/or sent to the first UE by the first processing apparatus and/or one of the one or more first APs (110, 208, 210, 212, 214, 216, 404), and wherein the method comprises, before determining whether an identifier of the first UE is associated with the first processing apparatus and/or one of the one or more first APs, assigning and/or sending the identifier to the first UE. 17. The method of any of claims 14 to 16, wherein the method comprises, if the number of further UEs is equal to or above the threshold number: determining, by the first processing apparatus (102, 104, 106, 108, 402, 1000), based on a channel quality of a channel between the one or more first APs (110, 208, 210, 212, 214, 216, 404) and each of a plurality of UEs that comprise the first UE (202, 204, 206, 408) and UEs served by the one or more APs, a UE with a lowest channel quality of the plurality of UEs; if the first UE is not the UE with the lowest channel quality, dropping, by the first processing apparatus, a connection with the UE with the lowest channel quality, and serving the first UE. 18. The method of claim 17, wherein, if the first UE (202, 204, 206, 408) is the UE with the lowest channel quality, rejecting, by the first processing apparatus (102, 104, 106, 108, 402, 1000), the connection request from the first UE. 19. The method of claim 18, comprising preventing, by the first processing apparatus (102, 104, 106, 108, 402, 1000), the first UE (202, 204, 206, 408) from connecting to any of the one of the one or more first APs (110, 208, 210, 212, 214, 216, 404) after rejecting the connection request from the first UE. 20. The method of claim 19, wherein preventing the first UE (202, 204, 206, 408) from connecting to any of the one of the one or more first APs (110, 208, 210, 212, 214, 216, 404) comprises rejecting subsequent requests from the first UE to join any of the one or more first APs. 21. The method of any of claims 14 to 20, wherein determining (504) whether an identifier of the first UE is associated with the first processing apparatus (102, 104, 106, 108, 402, 1000) and/or one of the one or more first APs (110, 208, 210, 212, 214, 216, 404) comprises determining whether the first UE will be served by one or more further APs, wherein one or more further processing apparatus processes signals for the one or more further APs. 22. The method of claim 21, wherein the first processing apparatus (102, 104, 106, 108, 402, 1000) is connected to the one or more further processing apparatus via backhaul. 23. The method of any of claims 14 to 22, wherein the one or more first APs (110, 208, 210, 212, 214, 216, 404) are connected to the first processing apparatus (102, 104, 106, 108, 402, 1000) via fronthaul. 24. The method of any of claims 14 to 23, wherein the further UEs comprise UEs that are also served by one or more further APs, wherein one or more further processing apparatus processes signals for the one or more further APs. 25. The method of any of claims 14 to 24, wherein the signals for the one or more first APs (110, 208, 210, 212, 214, 216, 404) comprise signals received by the one or more first APs and/or signals transmitted by the one or more first APs. 26. The method of any of claims 14 to 25, wherein the connection request (410) identifies the identifier of the first UE (202, 204, 206, 408). 27. A first processing apparatus (102, 104, 106, 108, 402, 1000) for processing a connection request from a first User Equipment, UE (202, 204, 206, 408), wherein the first processing apparatus processes signals for one or more first Access Points, APs (110, 208, 210, 212, 214, 216, 404), the apparatus comprising a processor (1002) and a memory (1004), the memory containing instructions executable by the processor such that the apparatus is operable to: receive (302) a connection request (410) for the first UE to connect to one of the one or more first APs; determine (304) whether an identifier of the first UE is associated with the first processing apparatus and/or one of the one or more first APs; if the identifier of the first UE is not associated with the first processing apparatus and/or one of the one or more first APs, determine (306) whether a number of further UEs served by the one or more first APs is below a threshold number, wherein the further UEs each comprise a UE that has an identifier that is not associated with the first processing apparatus and/or one of the one or more first APs; and if the number of further UEs is below the threshold number, serving (308) the first UE. 28. The apparatus of claim 27, wherein the memory contains instructions executable by the processor such that the apparatus (102, 104, 106, 108, 402, 1000) is operable to perform the method of any of claims 2 to 13. 29. A first processing apparatus (102, 104, 106, 108, 402, 1000) for processing a connection request from a first User Equipment, UE (202, 204, 206, 408), wherein the first processing apparatus processes signals for one or more first Access Points, APs (110, 208, 210, 212, 214, 216, 404), the apparatus configured to: receive (302) a connection request (410) for the first UE to connect to one of the one or more first APs; determine (304) whether an identifier of the first UE is associated with the first processing apparatus and/or one of the one or more first APs; if the identifier of the first UE is not associated with the first processing apparatus and/or one of the one or more first APs, determine (306) whether a number of further UEs served by the one or more first APs is below a threshold number, wherein the further UEs each comprise a UE that has an identifier that is not associated with the first processing apparatus and/or one of the one or more first APs; and if the number of further UEs is below the threshold number, serve (308) the first UE. 30. The apparatus (102, 104, 106, 108, 402, 1000) of claim 29, wherein the system is configured to perform the method of any of claims 2 to 13. 31. A system (400) comprising a first processing apparatus (102, 104, 106, 108, 402, 1000), one or more first Access Points, APs (110, 208, 210, 212, 214, 216, 404), and a first User Equipment, UE (202, 204, 206, 408), wherein the first processing apparatus processes signals for one or more first APs, wherein the system is configured to: send (502), by the first UE, a connection request (410) to connect to one of the one or more first APs; determine (504), by the first processing apparatus, whether an identifier of the first UE is associated with the first processing apparatus and/or one of the one or more first APs; if the identifier of the first UE is not associated with the first processing apparatus and/or one of the one or more first APs, determine (506), by the first processing apparatus, whether a number of further UEs served by the one or more first APs is below a threshold number, wherein the further UEs each comprise a UE that has an identifier that is not associated with the first processing apparatus and/or one of the one or more first APs; and if the number of further UEs is below the threshold number, serve (508), by the first processing apparatus, the first UE. 32. The system of claim 31, wherein the system is configured to perform the method of any of claims 15 to 26. |
Table 2 – Parameters and models employed in the simulations. Parameter Value s s In order to evaluate the performance of the proposed method, Figure 8 shows the average SE (Figure 8(a)) and average EE (Figure 8(b)) versus the number of UEs in a simulation of example methods of this disclosure, for Rician and Rayleigh fading channels. In this example, it is considered that ^ ^^^ = 10, there is a varying number of UEs (K), and 100 APs are deployed in the coverage area. It is noted from Figure 8(a) that for a channel modeled as a Rician Fading (i.e., with a line of sight, LOS, component), proposed methods can provide a slight improvement in the SE while providing gains for the EE, as Figure 8(b) shows. The EE gains can be up to 12.82% for 100 UEs, and the SE increase is related to the reduction of interference in the APs. As one of the effects of proposed methods is to reduce the number of UEs that the AP serves (as Table 3 below illustrates), the average number of interfering signals in each AP is also reduced. This reduction helps local precoding techniques such as LP-MMSE as their interference mitigation capabilities decrease with the number of UEs that the AP serves [2]. However, one can note small decreases in SE for proposed methods when the LOS components are blocked (Rayleigh fading channels), as Figure 8(a) depicts. Moreover, the EE gains are also smaller. The same behaviors remain by varying the number of APs (L) from 20 to 200. Keeping the number of UEs (K) fixed at 25 and considering ^ ^^^ = 10, proposed methods slightly increase the average SE (for Rician fading channels) and provide gains in the average EE. On the other hand, it also presents small SE decreases for Rayleigh fading channels. The impacts on inter-CPU coordination of example methods of this disclosure can be observed in Figure 9(a). It is possible to note that even if the number of UEs grows, the average number of inter-coordinated UEs served by the CPUs is the same, which makes the backhaul traffic independent of the total number of UEs for inter-CPU coordination. This differs from a UC cell-free system without presenting any control for inter-CPU coordination. For instance, the average number of inter-coordinated UEs per CPU grows proportionally to the number of UEs for the approach reported in [2], as shown in Figure 9(a). Figure 9(b) shows the cumulative distribution function (CDF) versus SE for a further comparison. It is noted that with proposed methods, not only significant degradations of the average SE are avoided, but also the CDF. Regarding the computational complexity of performing channel estimation and computing the precoding and combining vectors, proposed methods can reduce the average number of UEs served by an AP and the average number of APs serving each UE, as Table 3 below illustrates. According to [2], these quantities are critical for computational complexity, and the number of complex scalars exchanged with the fronthaul. Table 3 – Average number of UEs served by an AP and average number of APs serving each UE. Parameters setting: L = 100 APs, K = 25 UEs, ^ ^^^ = 10. M R P Figure 10 is a schematic of an example of an apparatus 1000 for processing a connection request from a first User Equipment (UE). The apparatus 1000 comprises processing circuitry 1002 (e.g. one or more processors) and a memory 1004 in communication with the processing circuitry 1002. The memory 1004 contains instructions, such as computer program code 1010, executable by the processing circuitry 1002. The apparatus 1000 also comprises an interface 1006 in communication with the processing circuitry 1002. Although the interface 1006, processing circuitry 1002 and memory 1004 are shown connected in series, these may alternatively be interconnected in any other way, for example via a bus. In one embodiment, the memory 1004 contains instructions executable by the processing circuitry 1002 such that the apparatus 1000 is operable/configured to receive a connection request for the first UE to connect to one of the one or more first APs; determine whether an identifier of the first UE is associated with the first processing apparatus and/or one of the one or more first APs; if the identifier of the first UE is not associated with the first processing apparatus and/or one of the one or more first APs, determine whether a number of further UEs served by the one or more first APs is below a threshold number, wherein the further UEs each comprise a UE that has an identifier that is not associated with the first processing apparatus and/or one of the one or more first APs; and if the number of further UEs is below the threshold number, serve the first UE. In some examples, the apparatus 1000 is operable/configured to carry out the method 300 described above with reference to Figure 3. It should be noted that the above-mentioned examples illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative examples without departing from the scope of the appended statements. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the statements below. Where the terms, “first”, “second” etc. are used they are to be understood merely as labels for the convenient identification of a particular feature. In particular, they are not to be interpreted as describing the first or the second feature of a plurality of such features (i.e., the first or second of such features to occur in time or space) unless explicitly stated otherwise. Steps in the methods disclosed herein may be carried out in any order unless expressly otherwise stated. Any reference signs in the statements shall not be construed so as to limit their scope. References 1. Hien Ngo et al., “On the Total Energy Efficiency of Cell-Free Massive MIMO,” in IEEE Transactions on Green Communications and Networking, March 2018. 2. Emil Björnson et al., "Scalable Cell-Free Massive MIMO Systems," in IEEE Transactions on Communications, July 2020. 3. Vida Ranjbar et al., "Cell-free mMIMO Support in the O-RAN Architecture: A PHY Layer Perspective for 5G and Beyond Networks,” in IEEE Communications Standards Magazine, April 2022
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