Chapter 11. HomeRF

The HomeRF consortium group was formed by a few PC and wireless technology companies during 1997. At that time, the IEEE 802.11 wireless Ethernet standards were just released and standards conforming transceivers were relatively too expensive for home applications. Goals of the HomeRF group were to develop an inexpensive wireless technology to connect not only PCs but also other popular electronic devices in a home environment. To reduce the development time, proven technologies, such as 802.11 and DECT (Digital Enhanced Cordless Telephone), were used as building blocks for the HomeRF specification also known as Shared Wireless Access Protocol Cordless Access [1]. The version 1.0 of the specification was released in January 1999. The HomeRF group has since grown to about 100 member companies. With the development of 802.11b, the demand for higher transmission throughput had led the HomeRF group to increase the signaling rate of its FHSS system so that it exceeds 1 MHz within the 2.4-GHz ISM band. With a favorable ruling on relaxed rules by the FCC, a higher throughput version of HomeRF version 2.0 was released in May 2001.

HomeRF 1.0 can provide transmission throughputs of about 0.8 or 1.6 Mbps for asynchronous data as well as up to four voice connections. The HomeRF transmission physical layer is based on the FHSS 2FSK (Frequency Shift Keying) and 4FSK technology defined by IEEE 802.11 standards. Under the CSMA/CA mechanism, the reception of every asynchronous data packet is acknowledged by a short packet. Voice connections to telephony devices, called I-nodes (where I stands for Isochronous), are established and managed by a Connection Point (CP). Each voice connection consists of a pair of downstream and upstream TDMA (Time Division Multiple Access) slots. Instead of an acknowledgment packet, the reception of a voice packet in the downstream is indicated by a bit in the header of the packet in the upstream direction. Voice packets are exchanged between the CP and I-nodes periodically in synchronization with frequency hops. Transmission of voice packets occurs right before each frequency hop, and retransmission of voice packets is allowed right after the frequency hop. The recently approved HomeRF 2.0 can provide higher transmission throughputs of about 5 or 10 Mbps using a signaling rate of 5 MHz in conjunction with 2FSK and 4FSK modulations.

In this chapter, the basics of HomeRF MAC are discussed in terms of a superframe structure, different types of MAC frames, and its encryption algorithm. Physical layer attributes of HomeRF 1.0 specification are then examined with respect to packet formats, data whitening methods, modulation parameters, and frequency hopping sequences. Some features of HomeRF 2.0 specification are also mentioned.