Tuesday, 27 October 2015

TDD-LTE-LTE-Interference Solution Based on CA

Incident Description (Incident Phenomena)
  Under CA-based scenario, CA based on inter-carrier scheduling is mainly used to solve the problem of control channel interference in hybrid networking among Macro cell and LPN cell, different cell sends control message using different carrier, service message can share the service channel. 
As the following figures shows, Pico cell in included within Macro cell, there are two carriers in Macro cell,  f1 and f2.
·            Around the region of Non-Pico cell, data and control signaling for MUE are sent on f1 and/or f2. 
·            Around the region of Pico cell, control signaling for Macro cell MUE is sent on f1, control signaling for Pico UE is sent on f2. While for data message, downlink interference coordination will be used. R8/9 terminal can be scheduled on a part of sub-carrier, terminal support R10 can be scheduled on multi-carriers ( e.g. control message on f2, data on f1).
Figure 27 Solution of inter-cell control channel interference suppression based on CA
 
 Solution
 CA with the character of inter-carrier scheduling can avoid interference between Macro cell and Micro cell in Hetnet scenario, especially for control channel avoidance. As the following figures show, UE’s PDCCH in Micro cell and Macro cell can distribute onto different component carrier to avoid cell edge users’ intra frequency interference, hence to improve cell edge user’s performance.Figure  28  Cases of scheduling based on inter-carrier
 
The advantage of ICIC based on CA is convenient to do interference coordination for control channel, or if don’t adopt control channel interference coordination, send the control channel message on good quality carrier, and hence to enhance the control channel transmission robust. In addition, in Marco/Micro Hetnet scenario, by CA, it is convenient to avoid the problem of control channel interference. So in interference limited scenario, inter-carrier UE scheduling is considered. But it is need high complexity of software to implement inter-carrier scheduling, signaling overheads increased, and there increased 3 bits CIF on the basis of original DCI size, there also required terminal capability, and overload of control channel is also increased. The more UE in inter-carrier scheduling, the more control channel resource limited, and hence influence the whole network throughput.

Budi Prasetyo

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