Optimal Frequency and Slot Assignment for MAC Layer Protocol in a Hybrid Narrowband and Wideband Physical Layer Con guration in an SDR

Abstract

In order to ful ll military operational requirements, wideband and narrow- band waveforms are needed. Most of the vehicle-mounted, rotor and xed systems use narrowband waveform with 25kHz bandwidth to operate in a tactical zone instead of wideband waveform because of its poor propagation. For majority of military systems, a single narrowband channel of 25 kHz bandwidth is used with TDMA as MAC protocol. Using TDMA for MAC protocol results not only in delays in communication because each node has to wait for its assigned slot to communicate but also a huge spectral range remains unused. Software de ned radio either uses narrowband or wideband mode, this research proposes a hybrid mode where all transmitters trans- mit in narrowband and receiver receives all these simultaneous narrowband signals in wideband reception. Instead of one narrowband channel, system operates on multiple channels with con ict free FDMA based channel alloca- tion protocol. Using time division and frequency division hybrid approach, multiple radios transmit at the same time that not only increases spectral e ciency but also enhances performance of the system. Receiving multiple narrowband signals instead of single narrowband not only increases through- put of the system but also closing the control phase in a shorter time period. The system uses one control channel and multiple data channels of 25 kHz bandwidth. Nodes autonomously detect any change in network topology in minimum time by using local topology knowledge only. Nodes rst approach control channel of known frequency and after frequency allocation, they move to separate data channels for data transmission. First phase of research fo- cuses on physical layer feasibility and performance analysis of the proposed scheme. Second phase includes implementation of optimal frequency and slot assignment hybrid protocol for MAC layer in order to use simultaneous nar- rowband waveform in wideband multiple access. The main contribution of proposed technique is designing a protocol that utilizes unused wide spectral range e ciently and increases data rates for multiple hops mobile nodes to reduces call setup delays as compared to traditional TDMA protocols.