Abstract
Short-range wireless technologies are known to transmit voice, audio, image, and video messages in real time. Energy consumption and transmission reach are critical in such networks, especially for portable and power autonomous devices. The purpose of the Voice over Zigbee technology is to provide a competitive offering that excels in these performance aspects. Due to the CSMA-CA mechanism implemented in the 802.15.4 layer, a well-designed strategy must be considered in Zigbee to create a robust, reliable, and full-duplex conversation. In past efforts, we proved that the radio channel of Zigbee has enough bandwidth to support a full-duplex conversation with narrow-band voice codecs. Our embedded implementation of the Speex voice codec targeted the development of a low-cost, ultralow-power, long-range wireless headset using Zigbee technology to transmit voice in full-duplex mode for use with leading PC VoIP programs. Furthermore, we presented the real environment performance evaluation and power consumption tests involving the developed headset prototype. Talk time is comparable to Bluetooth including at the power budget, the codec processing, and analogue audio interface, but its deep-sleep lifetime more than doubles the Bluetooth performance. This was one of the very few successful efforts to port a voice codec on an ultralow-power DSP for use with power sensitive Zigbee applications, which is highly cited in the literature, proving additionally that using an open-source codec can deliver similar voice quality, reducing the total system cost. The current paper elaborates on the embedded parallelism of the Speex implementation and the exploitation of the DSP architectural parallelism which critically enabled the Voice over Zigbee application on the ultralow-power DSP platform. Another significant contribution of this work is towards understanding and resolving the challenges faced when trying to achieve good quality transmission of media over constrained devices and networks. The way to new ultralow-power voice-related Zigbee and constrained network applications is open.
Highlights
Few approaches can be found in the literature that examine the possibility of 802.15.4/Zigbee networks supporting voice transmission, either through simulation or based on already deployed networks (e.g., [1,2,3,4]). e general conclusion drawn from previous work is that voice can be carried over Zigbee; there exist several restrictions in terms of available bandwidth and network topology
The radio channel of Zigbee has enough bandwidth to support a full-duplex conversation with narrow-band voice codecs
Work e Zigbee standard is designed to enable the deployment of low-cost, low-power wireless sensor and control networks based on the IEEE 802.15.4 physical radio standard
Summary
Zigbee is a wireless standards-based technology that addresses the needs of sensory network applications, enabling broad-based deployment of complex wireless networks with low-cost and low-power solutions that run for years on inexpensive primary batteries. e raw data rate of this technology at 2.4 GHz, 250 kbps is low compared with other wireless technologies, but sufficient to transmit voice using narrow-band voice codes. E general conclusion drawn from previous work is that voice can be carried over Zigbee; there exist several restrictions in terms of available bandwidth and network topology. E Eurostars Z-Phone project goal was to develop a low-cost, ultralow-power, long-range, ergonomic wireless headset using Zigbee Technology to transmit voice in fullduplex mode for use with leading PC VoIP programs (e.g., Skype and Messenger), in addition to a USB-Zigbee bridge module and a PC driver [5]. E initial objectives were to achieve 2x communication autonomy and 4x distance compared with Bluetooth technology. E paper summarizes the results of our previous work regarding the design, implementation, and validation of the Z-Phone architecture and the headset system and presents the details of the embedded parallelism which made the application feasible in the constrained environment. Important future work items are presented in the conclusions section
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