Design of Multi-carrier and Multi-protocol Picocells

Published:2011/9/2 1:49:00 Author:Phyllis From:SeekIC

With the widespread of smart phones, web tablets, and laptops, the capacity and coverage upgrades of existing mobile access networks need to improve to meet the requirement of high mobile data rates. Now, most of the subscribers are using the 3G networks, which remark the transition process from 3G-to-4G service.

Products that enable operators to deploy this capacity will be silicon-based small cells that also known as system-on-chip-based picocells and relays that can easily be deployed in indoor and outdoor locations.

Picocells are featured in low compact and passive cooling, so the SoCs need to ensure very low system-level power consumption. Also these SoC platforms need to integrate all processing layers for each supported protocol to support the design of cost-effective, easily mountable, single-chip products. The present W-CDMA and LTE require sufficient processing capacity to support high-capacity mobile data services.

LTE requires the support of 2x2, 2x4 and ultimately 4x4 RF configurations with SoC-embedded multi-channel antenna array and multi-carrier digital RF front-end functionality. Operators are resorting to deploy 2x5 MHz channel configurations with MIMO as W-CDMA networks are struggling to meet mobile data demand.

Sufficient independent processing and hardware acceleration cores must be available on all processing layers in the SoC platforms, enabling the isolated operation of all protocol layers for each supported service access technology. SoCs must operate with sufficient spare capacity on each processing layer, and individually for each service access technology.

In fact, the deployment site dictates many of the configuration parameters of a picocell product as a consequence of cell size and demography surrounding the location, and as a result of physical and mounting restrictions for any specific installation site.

The requirements for simultaneously registered, active subscribers and required RF output power to cover the service area are driven by cell size and demography. The actual mounting location will determine the requirements for cell-site backhaul, specifically in the context of high-density small cell deployments in outdoor locations, such as lampposts, traffic lights, or side walls of buildings. While wire line fiber-optic or copper access is preferred, it is not readily available in these locations, and building permits, as well as construction time and costs, quickly erase operators’ business case. Hence, wireless backhaul is critical for deployment of picocells in such locations.

Low-cost wireless backhaul must be integrated with the picocell product, as many of these locations do not permit systematic deployment of two pieces of equipment. Hence, it is essential that the SoCs used for picocell products support suitable wireless self-backhaul (sub-6GHz, or E-band) operating concurrently with W-CDMA and LTE service access. This can be facilitated by means of dedicated self-backhaul technology, e.g. in W-CDMA picocell deployments, or utilizing standard LTE Advanced relay technology. Each option requires integrated sub-6 GHz NLOS or E-band LOS RF subsystems.

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