CoMP (2): CoMP Coordination Areas Defined in 3GPP (7 Scenarios)

August 19, 2014 | By Dr. Michelle M. Do and Dr. Harrison J. Son (tech@netmanias.com)

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In the CoMP scenarios defined in 3GPP Release 11¹ and Release 12², CoMP is used

within a single eNB (intra-eNB) with ideal backhaul only - in restricted areas in Release 11
among eNBs (inter-eNB) with non-ideal backhaul as well - in more expanded areas in Release 12

According to NGMN³, ideal backhaul refers to one with latency of 2.5 usecs or less and capacity of 10 Gbps or higher, whereas non-ideal backhaul refers to one with latency of 5~30 msecs (or even higher).

Release 11 and Release 12 have defined 4 and 3 scenarios, respectively. We will refer to them as scenario 1 through 7, and explain them one by one below.

Figure 1. CoMP coordination areas defined in 3GPP scenarios (Release 11 and Release 12)

■ Release 11 CoMP Scenarios: Intra-eNB CoMP in Ideal Backhaul (Coordination among Cells that Belong to the Same eNB with Ideal Backhaul)

In Release 11, CoMP can be used only within the coverage area of a single base station (eNB). The coverage area of one base station can be as large as to include only one site (e.g. macro eNB 2/cell site 3 in Figure 1), or can be extended to include many sites (e.g. macro eNB 1/ cell sites 1 and 2). In Release 11, CoMP coordination is possible only among neighbor cells belonging to the same base station (i.e. intra-site cells or inter-site cells). Cells do not coordinate with their neighbor cells if they belong to different eNBs. That is, CoMP coordination is performed within one eNB only (intra-eNB CoMP). Release 11 defined the scenarios for intra-eNB CoMP in ideal backhaul as follows:

Scenario ❶: CoMP used among macro cells belonging to one site in one macro eNB (e.g. Cells 2 and 3 in Cell Site 1) - intra-site

Scenario ❷: CoMP used among macro cells belonging to different sites in one macro eNB (e.g. Cell 2 in Cell Site 1 and Cell 4 in Cell Site 2) - inter-site

Scenario ❸: CoMP used between a macro cell and one of its small cells (small RRHs) that has a different cell ID than the macro cell

Scenario ❹: CoMP used between a macro cell and one of its small cells (small RRHs) that has the same cell ID as the macro cell

Release 11 allows for intra-eNB CoMP only. Due to this restriction, CoMP standardization in Release 11 is defined only for physical layer operations, and not for interfaces between eNBs. Each eNB uses a vendor-specific CoMP algorithm, and vendor proprietary interfaces are used between base stations. So, CoMP coordination between eNBs with different vendors is not possible.

■ Release 12 CoMP Scenarios: Inter-eNB CoMP in Non-Ideal Backhaul (Coordination between eNBs with Non-Ideal Backhaul)

To be able to apply Release 11 CoMP scenarios in more base stations, ideal backhaul that connects all base stations and all sites with optic fibers, and hence causes no latency is required. Practically, however, few operators can provide such ideal backhaul. To address this issue, in Release 12, CoMP scenarios and technologies have evolved to coordinate with neighbor base stations in non-ideal backhaul networks - more practical network environments - like Microwave, DSL, Cable, PON, etc. Release 12 defined the scenarios for inter-eNB CoMP in non-ideal backhaul as follows:

Scenario ❺: CoMP used among macro cells belonging to different macro eNBs (e.g. Cell 3 in eNB 1 and Cell 7 in eNB 2)

Scenario ❻: CoMP used between a macro cell and one of its small cells (small cell eNBs)

Scenario ❼: CoMP used among small cells (small cell eNBs) in a macro cell (macro cell and small cells use different channel, but small cells share the same channel)

■ Reducing Interference Areas by Expanding Coordination Areas (Only CoMP between macro cells is presented below)