Channel Access for Simultaneous Voice and Data Transmissions in a Multiple-hop Packet Radio Network

A new programmable radio has been designed by ITT and in a companion paper [1] we describe new channel-access protocols that are specifically designed for this radio. The protocols described in the companion paper support a network organization in which all the radios are within communication range. In this manuscript we suggest some extensions to the waveform and the channel-access protocol that allow the network to support a multiple-hop topology. The waveform extensions allow a radio to transmit or receive voice messages with a group of radios and simultaneously exchange data messages with a radio that is not part of the group, The channel-access protocol enables a radio to set up the interleaved transmissions and allows the radio to relay data packets. The protocols are implemented in OPIVEZ a computer aided design tool, and the network perjlormance is evaluated using the different waveform and channel-access protocol options. INTRODUCTION Integration of data networking and packet radio protocols into traditional voice only systems, such as SINCGARS and HAVEQUICK, is necessary to meet evolving multimedia communication requirements. The success of this integration is dependent on the development of improved channel-access and network protocols, which allow for simultaneous voice and data information transfer. In [1] an overview of the complete system design is given, including a description of a new waveform format that supports integrated voice and data transmissions. The system described in [1] focuses on the channel access required for a network where all radios are within direct communication range. In this manuscript we extend the channel-access protocols to improve the ability to support a mobile, multiple-hop packet radio network. The channel-access protocol is designed to allow radios that are involved in transmitting or receiving voice packets to also receive or transmit data packets. Therefore, a radio processing voice packets is not blocked from handling data packets. The protocols also allow for the use of two different fi-equency hop schemes. The first method requires the transmitter or receiver of voice packets to maintain the hopping pattern during idle periods between voice packets. The other method allows for the hopping pattern to change during these idle periods. An OPNET simulation is implemented to characterize the performance of these protocols, and we show that improved network performance is achieved because of the new channel-access schemes for simultaneous voice and multiple-hop data operation. WAVEFORM FORMAT In this section we describe two extensions to the basic slow frequency hop waveform formats that are available in ITT’s programmable radio platform (PRP). The two new versions of these waveforms are denoted as Data-Only-V+D and V+DInclude. These waveforms are utilized by the channel-access protocol when a radio is communicating with a group of radios that is not fully connected. Before describing these waveforms, we briefly review the three basic PRP waveforms. Additional details about these waveforms are found in [1]. The Data-Only waveform is illustrated in Figure 1, and it allows an idle radio to broadcast a data message to one or more idle radios. This waveform consists of a multiple-hop synchronization preamble followed by a data message that is encoded into one or more data frame error control blocks (ECB). A data frame is 32 dwell intervals long, and it contains one ECB. Data Data Frame I ‘CBI***= Data Frame synch ECB Figure 1. Data-Only Waveform The V+D waveform structure, illustrated in Figure 2, is employed to broadcast a voice message, In addition, a radio can use this waveform to transmit data messages during the idle periods of a voice transmission.