0 Paper on " A High Data Rate Frequency Hopping Modulation Scheme "

ABSTRACT

There is a need to select the 'first step up' modulation scheme for higher data rate frequency hopping systems.  This is seen as one step in a longer journey where considerably higher data rates are used.  In order to make this progression viable, the first step should be taken with a well proven modulation scheme.  An equally important factor is implementation, this higher rate must not preclude the use operation of GFSK, and all in a PCMCIA type II form factor.  This note shows that */4 DQPSK can serve all these needs.

INTRODUCTION

One of the great advantages of the proposed modulation scheme is that design and development can start now, there is no need of technology transfer from a single source or the need to prove a modulation scheme.  A complete description of */4 DQPSK is given.  The detail here is sufficient to enable the design and development of systems.  It is clearly a modulation scheme that is bandwidth efficient and enables good performance at low cost, hence its selection for the Japanese digital cordless telephone standard.
Ideally with a wireless product, there is freedom for the manufacturer to balance cost versus performance, */4 DQPSK has this ability, one can select to develop the 'ideal' system or a lower cost system with very reasonable performance.The higher data rate inputs have been focused on the use of non linear amplifiers.  However this places serious constraints on the data rate achieved or degrades the performance of the radio link.  Technically the only route to achieve higher data rates without significant loss of performance is to follow the route of non constant amplitude envelope modulation.  One advantage of */4 DQPSK is that 'reasonably linear' transmit amplifiers can be used that have acceptable efficiency, not as poor as those assumed to date.
This paper proposes 1.5Mb/sec, not because this is the limit, but because of system implementation issues.  This note is a general discussion as to why this modulation scheme should be selected, additional technical information will be presented in Vancouver.

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