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Copyright © 2012, Random Access for M2M Communications over LTE network.

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Presentation on theme: "Copyright © 2012, Random Access for M2M Communications over LTE network."— Presentation transcript:

1 Copyright © 2012, Random Access for M2M Communications over LTE network

2 Copyright © 2012, Outline Problem Statement Related work Proposed Design References

3 Copyright © 2012, Problem Statement To enable full mechanical automation where each smart device can play multiple roles among sensor, decision maker, and action executor, it is essential to construct scrupulous connections among all devices [1] In the literature, few realizations of M2M communications have been proposed, such as leveraging Bluetooth (IEEE ), Zigbee (IEEE ), or WiFi (IEEE b) technology. However, there is still no consensus on the network architecture of a general scenario for M2M communications [1]

4 Copyright © 2012, Problem Statement It is one of the key issues in the 4-th generation (4G) cellular networks how to efficiently handle the heavy random access (RA) load caused by newly accommodating the huge population of Machine-to-Machine or Machine-Type Communication (M2M or MTC) customers/devices [2] Supporting trillions of devices is the critical challenge in machine-to-machine (M2M) communications, which results in severe congestions in random access channels of cellular systems that have been recognized as promising scenarios enabling M2M communications [3]

5 Copyright © 2012, Related Work Design focus/improvementsUE mixed with MTC Grouping-based radio resource management [1] MTC devices are grouped to guarantee the QoS requirement Yes ABC [2] Using different combination of H2H and M2M’s preamble testify the system’s performance Yes Cooperative ACB [3] Minimize the maximum number of access among M BSs No Proposed design 1.Balance the number of access among M BSs 2.MTC will not interfere UE during random access procedure 3.MTC devices are grouped to reduce the random access delay Yes

6 Copyright © 2012, Proposed Design Problem formulation [3]  Consider the random access of M2M communications in LTE-Advanced with BSs indexed by = 1,..., and active MTC devices indexed by = 1,...,  Distinct from the ordinary ACB that each MTC device can only access the BS attached by the MTC device, in this letter, we propose that an MTC device is able to access the BS unattached by the MTC device when the MTC device locates within the overlapped coverage area of multiple BSs

7 Copyright © 2012, Proposed Design  To formulate such a random access problem, we adopt following notations 1)Denote as the set of MTC devices attaching to theth BS and ∥∥ as the norm of. When cooperation of BSs are available, for all m are known by all BSs. Note that

8 Copyright © 2012, Proposed Design 2)Denote as the set of BSs that the th MTC device can possibly access. The th MTC device selects one BS from to proceed to the random access. In LTE-Advanced, the BS can request the MTC device to perform the exploration of surrounding BSs, and report the exploration result. Thus, for all are available for all BSs. However, for = 1,...,, != are unknown by the th MTC device for = 1,...,.

9 Copyright © 2012, Proposed Design 3)Denote as the set of MTC devices that access the th BS. In the ordinary ACB, ∥∥ for all are known by each BS. However, if each MTC device can access the BS unattached by the MTC device, ∥ ∥ for all are random variables unknown by BSs, unless the BS selection strategy of each MTC device is given 4)Denote l, as an indicator function that, for the th MTC device,

10 Copyright © 2012, Proposed Design 5)Denote ′ as the set of MTC devices that can only receive the signal from the th BS and these MTC devices can only access the th BS. ∥ ′ ∥ is the norm of ′

11 Copyright © 2012, Proposed Design

12 Copyright © 2012, Proposed Design  In the ordinary ACB, although the throughput of each cell can be individually maximized by individually setting p = 1/ ∥∥ (where p is the ACB parameter of the the th BS) in each BS, the delay experienced by an MTC device attached to the th BS may be unacceptable when requires to be set to an extremely small value under a large ∥∥  our objective is to provide an optimum control of a set of ACB parameters p = [1,..., ] jointly decided by BSs to minimize the largest access delay experienced among active MTC devices

13 Copyright © 2012, Proposed Design  Through cooperation among BSs to make a joint decision of p = [1,..., ], the problem can be formulated by

14 Copyright © 2012, Proposed Design BS selection strategy for each MTC device  BS selection strategy is based on pm, for m=1,…,M (BS with higher pm has higher probability to be accessed by MTC)  Upon receiving ˜p = {,,..., } ⊆ p, the th MTC device adopts the strategy where, is the probability that the th MTC device selects the th BS to access

15 Copyright © 2012, Proposed Design Cooperative Access Class Barring  Given that the strategy on the selection of the BS in each MTC device in (3) is known by BSs, ∥∥ for all can be obtained by  The optimal p can be found by algorithm 1 and algorithm 2 proposed by [3]

16 Copyright © 2012, Proposed Design

17 Copyright © 2012, Proposed Design

18 Copyright © 2012, Proposed Design

19 Copyright © 2012, 王老師的建議 1. 如何更精確反應出每個 BS 下的情況 ? Key paper 所提的 Qn,i 只考量了此 round 期望能 access BS 的 MTC 數,逸懷的方法加入考量每台 BS 實際有 attach 上此 BS 的個數,更能反應出目前 BS 實際 loading 情況 2. Access Barring Check(ABC) 與 Access Class Barring(ACB) 的差別 ? ABC 與 ACB 都是根據目前 BS 的 loading 來調整其 threshold , 所以沒有差別

20 Copyright © 2012, 曾老師的建議 1. 可衡量 MTC 與 UE 通過 Random access 的比率 2. MTC 與 UE 在 Random access 時,是共享 or 獨有 Resource Block(RB)? 目前 3GPP spec 並沒有針對這部分做規範,但根據 survey paper ,目前研究都是假設 MTC 與 UE 在 Random access 時是 共享 RB 3. UE 及 MTC 發 Random access 的頻率 ? UE 發完 Random access 與 BS 連上後,就不再發 Random access MTC 每次的上傳或是下載前,都要先跟 BS 發 Random access

21 Copyright © 2012, References [1] Shao-Yu Lien; Kwang-Cheng Chen; Yonghua Lin;, "Toward ubiquitous massive accesses in 3GPP machine-to-machine communications," Communications Magazine, IEEE, vol.49, no.4, pp.66-74, April 2011 [2] Ki-Dong Lee; Sang Kim; Byung Yi;, "Throughput comparison of random access methods for M2M service over LTE networks," GLOBECOM Workshops (GC Wkshps), 2011 IEEE, vol., no., pp , 5-9 Dec [3] Shao-Yu Lien; Tzu-Huan Liau; Ching-Yueh Kao; Kwang-Cheng Chen;, "Cooperative Access Class Barring for Machine-to-Machine Communications," Wireless Communications, IEEE Transactions on, vol.11, no.1, pp.27-32, January 2012

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