Question

What are the uses of distributed antennas in communication systems? How can you relate distributed antennas with coordinated multipoint (CoMP) transmission and reception in LTE-Advanced systems?

Answer 1

• The concept of a Distributed Antenna System, DAS, has many advantages in some applications. A Distributed antenna system, DAS is a network of antennas spaced apart but connected to a common source. In this way, the DAS can provide wireless or radio coverage within a given area.

• Advanced interference mitigation techniques relying on multipoint coordination have attracted significant attention from the wireless industry and academia in the past few years. In 3GPP LTE-Advanced, a work item on Coordinated Multiple Point transmission and reception (CoMP) was initiated in September 2011, and it is one of the core features of Release 11. This work item aims to provide the necessary specification support to efficiently realize the benefits of cooperative transmission in the downlink and cooperative reception in the uplink. This article discusses the specification support for CoMP and the motivations behind the specific design choices. The deployment scenarios that were considered for the application of CoMP in Release 11 are also presented.

Answer 2

A Distributed Antenna System(DAS) can be designed for use indoors or outdoors and can be used to provide wireless coverage in hotels, subways, airports, hospitals, businesses, roadway tunnels etc. The wireless services typically provided by a DAS include PCS, cellular, Wi-Fi, police, fire, and emergency services.

Distributed antenna systems do not create a signal, they simply amplify the original carrier sources throughout the property through strategic antenna placement. Elements of a DAS can include a main antenna on the roof, a Base Transceiver Station (BTS), or portable nodes called small cells.

Coordinated Multi-Point transmission and reception (CoMP) refers to a wide range of different techniques with the common denominator being the dynamic coordination of transmission and/or reception at multiple geographically separated sites with the aim to enhance system performance and end-user service quality. CoMP can be seen as an extension of the inter-cell interference coordination that is already part of LTE.

Joint reception means that the signals received at multiple sites are jointly processed for enhanced reception performance. Joint transmission implies that data is transmitted to a mobile terminal jointly from several sites, thereby not only reducing the interference but also increasing the received power. Both joint reception and transmission pose high requirements on low latency in the communication between the network node involved in the joint processing and the different antennas involved in the reception/transmission.