Some of these will make it into the final standard and some will not. Nevertheless, one thing that is sure is that LTE-Advanced will bring a new radio network and the implied costs and deployment issues that come with any new system - right on the heels of LTE. So, the timing of its arrival is by no means certain. On the other hand, competition forces operators and vendors to keep investing in new technologies to provide a better user experience for customers at lower costs, which is what LTE-Advanced will do.
Perhaps the most interesting and likely to be approved enhancements will be support of wider transmission bandwidths, advanced multi-cell transmission/reception technologies and the concept of relay nodes.
Wider bandwidths up to 100 MHz will be supported with either continuous or discontinuous spectrum. Continuous spectrum usage will require frequency allocations in new bands, such as 3.4 to 3.8 GHz. Wider spectrum is required to increase the bits-per-Hz performance and achieve the desired peak data rate of 1 Gbps on the downlink. Discontinuous bandwidth can be implemented within current spectrum allocations, but it will require several receivers to be built in to the UE. This will have to be balanced against increases in UE size, cost, and power consumption.
Coordinated multipoint transmission/reception can be used to increase frequency efficiency and cell edge user throughput. One proposed technology to realize this is use of RRE (remote radio equipment), this would enhance ICI (inter-cell-interface) management and handover performance.
Various concepts of relay nodes are also being proposed, and are beneficial for coverage extensions. L1, L2 and L3 relay nodes are proposed. L1 relay nodes are like traditional repeaters as we see in 2G and 3G networks, whereas L2 and L3 relay nodes use different frequency/time resources and can achieve wider coverage extensions via increases in signal to noise ratio.
LTE and LTE-Advanced are becoming the de facto standards for future telecommunication. As such, LTE looks like it will enjoy a robust and rich ecosystem. Thus an almost inevitable path to LTE-Advanced has already been set.
Juha Ristimaki is with the Asia-Pacific Technology Group of Nokia Siemens Networks