LTE Advanced: 3GPP Solution for IMT-Advanced

9.8 Summary

Relay nodes are targeted to improve user data rates for cell edge users and other users with poor radio coverage, including indoor users. Relays are defined in 3GPP Release 10 and they are backwards compatible allowing Release 8 terminals to connect to relays. The relay node looks like a normal eNodeB from the terminal point of view. The relay node supports full eNodeB functionality including encoding, decoding and packet scheduling. The access link in the relays can use the same frequency (inband) or different frequency (outband) as the backhaul link. In case of inband relays, the access and backhaul links are separated in the time domain to avoid any interference issues between the two links. The relay nodes are therefore clearly easier to deploy than traditional RF repeaters from the interference point of view. The resource allocation between access and backhaul links can be adjusted according to capacity requirements.

The simulations show that relay nodes bring a substantial improvement in the cell edge user data rates. The benefit is highest when the relay node can be placed close to the user thus providing good signal -to-noise ratio. The system capacity will also benefit if the quality of the backhaul link is good because it allows minimizing the capacity allocation for the backhaul and giving more capacity for the access link and the users served by the donor eNodeB. The relay node brings the largest benefit for the operator if the backhaul cost of the traditional ...