Adaptive Techniques for Tactical Communication Systems

In the future Swedish Defence the capacity requirements on the communication network is expected to be substantially increased. To satisfy these demands, high capacity radio nodes must be developed. The communication system should also be able to work in different communication environments. To provide robustness and capacity in diverse environments, it would be preferable with dynamic flexible radio nodes. The goal with an adaptive radio node is to be able to adjust the parameters of the radio transmitter and receiver, when changes in the tactical scenario, radio channel conditions, signal environment or service demands have occurred, so that the best possible performance is obtained. Orthogonal Frequency Division Multiplexing (OFDM) is a promising technique for tactical communication systems since it is flexible and can be adjusted to a number of different scenarios. In this work we have examined the use of adaptive techniques for an OFDM-system. Two different adaptive modulation approaches for an OFDM-system, as well as different modulation group sizes (i.e. the number of neighbouring sub-carriers employing the same modulation), are evaluated through simulations. The influence of delays in the feedback loop is also investigated. Results from simulations with two different diversity techniques combined with adaptive modulation are also presented. The investigated diversity techniques are: space diversity in the receiver with maximal ratio combining (MRC) and transmit diversity with space frequency block coding (SFBC). See also ADM202750. Published in Military Communications (Les communications militaires), RTO-MP-IST-054, paper no. 9, p9-1-9-16, 2006. Presented at the Information Systems Technology Panel (IST) Symposium held in Rome, Italy on 18-19 April 2005. Document includes briefing charts (19 slides, title same as report). The original document contains color images.