Cloud RAN vs. Picocells: The Need for Integrative Approach in Next Generation Network Design.

Picocell vs. Cloud RANWhen it comes to deciding on deploying small cell base stations, one is faced with a few options. One option is based on cloud RAN architecture with remote radio heads connected through optical fiber to a central base station housing the baseband processing. A second option is that of a compact base station which includes both the radio frequency and baseband processing functions. The compact base station is connected to the core network by a number of different backhaul technologies.

The availability of low cost fiber is a gating factor in deploying cloud RAN architecture. Remote radio heads require very high capacity links to support modern air interface features such as multiple antennas for MIMO. CPRI and OBSAI interfaces run at between 3 and 6 Gbps depending on the number of supported antennas. The compact base station on the other hand requires much lower capacity for backhaul – on the order of tens to over a hundred Mbps.  Low backhaul throughput requirements should translate into lower deployment cost to the advantage of compact base stations. Read more of this post

Should Small Cells Be Deployed In Their Own Spectrum Band?

Small cells raise a number of practical implementation questions which are yet to be resolved. One such question is whether small cells should operate in the same frequency band as the macrocell layer (co-channel deployment), or on a different frequency band. The question has profound implications to operators, vendors, and to regulators alike.

To clarify, recall that in co-channel small cell operation interference between the macrocell and small cell layers limit the capacity gain of small cells. The benefit from small cells is realized when they are placed in traffic hot spots whose location must be identified (which is a challenge in itself). As LTE technology matures with advanced releases, techniques such as ‘Almost Blank Frame‘ are introduced to manage interference whereby a layer temporarily ceases operation to reduce interference to the second layer as shown in Figure 1. These techniques largely trade off some capacity for lower interference (but not network capacity: network capacity would still increase because small cells are added).  Using a different frequency band for small cells provides yet higher capacity because the different layers are separate networks. Read more of this post