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.
