Zigbee Phone With The Voip Voice Processing Technologies

The ZigBee specification, called the next revolution for wireless technique, promoted at Dec. 2004, is a standard that defines a stack protocol enabling the inter-operation of wireless devices in a short-distance, low-cost, low-power consumption and low-data-rate network. This technique provides a series of standard specifications, three working bandwidths, some configurable network and security functions. The ZigBee stack is founded over the IEEE 802.15.4 standard, which defines the multiply accumulate (MAC) and physical (PHY) layers of the protocol.Today, Voice over Internet Protocol (VoIP) has developed rapidly all over the world and implemented most of traditional Public Switched Telephone Network (PSTN) functions. But as the inherent trait of delay and lack of bandwidth on the Internet, the speech quality of VoIP, which once obstructed the development of VoIP, is not as good as desired. So it is necessary to develop speech processing techniques such as speech compression, auto echo cancellation (AEC), auto gain control (AGC), jitter buffer and forward error control (FEC) etc. to improve the speech quality.The connection of ZigBee and VoIP makes the application of ZigBee extend to voice processing. The author took part in implementing a ZigBee phone with VoIP under the platform provided by Freescale Company. This phone includes two parts: the gateway and the handset. The gateway is based on Freescale MCF5235EVB and embedded Configurable operating system (eCos), using VoIP to communicate. The handset is base on Freescale MCF5213EVB and uC/OS II, using ZigBee to communicate with the gateway and then get to outside. This design is very valuable and practical for the application of ZigBee and VoIP.This paper first introduces the ZigBee protocol and VoIP briefly, then describes two audio compressing systems, the Enhanced PCM and 16-bit ADPCM system, after that the technique of the Quality of Service (Qos) in the system is discussed, finally, the designing methods, implementing and testing results on the ColdFire target platforms are presented.