Modern DAS systems on offer today are rising to the challenge from small cells by building on their inherent advantages of neutral host, and macrocell parity and adding features such as traffic steering and the ability to converge multiple networks (for example Wi-Fi or public safety) on the same in-building backhaul. They are also tackling one of the main drawbacks – cost per sq. foot of installation and OPEX needed for system cooling and operation.
Small cells challenge DAS by offering higher capacity and low cost/sq. foot and OPEX advantages. However, small cells do not immediately provide a neutral host capability and are complex to configure since the baseband, unlike DAS, is distributed in each small cell which must coordinate with its neighbor to mitigate interference. Techniques such as eICIC (enhanced Inter Cell Interference Coordination) or CoMP (Coordinated Multi Point) are specified by 3GPP and continue to evolve but are complex. Small cells on offer from tier1 vendors today increasingly offer macro parity and Wi-Fi integration as a challenge to DAS.
Hybrid systems are a recent development where the best of DAS and small cells merge. These systems centralize the baseband function like DAS but use CRAN (Cloud RAN) techniques to distribute CPRI signals over dedicated fiber to remote radio heads in the building. In this way the baseband remains centralized but the radio function is distributed.
As the demand continues to explode for in-building coverage and capacity there are innovations that are occurring in DAS, small cells and DRS which will allow them to coexist with the macrocell RAN (Radio Access Network) in a true Heterogeneous Network or HetNet.
This report examines the advantages and disadvantages of each of these in-building wireless systems and discusses examples of each from 17 vendors, 9 of which are traditional small cell vendors and 8 of which are DAS vendors.
The small cell vendors discussed are: Airvana, Alcatel-Lucent, Cisco, Ericsson, Huawei, ip.access, NEC, Nokia and SpiderCloud. The DAS vendors we discuss are Axell, Commscope, Corning, Dali Wireless, Kathrein, SOLiD, TE Connectivity, and Zinwave.