Vadim Olshansky
Ee206a
Spring 2001
Hw #1
Question #2
1. Introduction
2. Technical Summary
3. Comparison with similar technologies
4. Links
1. Introduction
Recently, a variety
of different technologies have emerged to facilitate easy connectivity
among various devices providing access to data, multimedia, and
voice communications. Traditional technologies utilized wired
medium to interconnect devices. However, the latest technologies
aim to provide data and voice communications over wireless medium
such as radio frequencies. This abviates the need for cables and
allows easy mobility and flexibility. Cordless and PCS phones
already utilize wireless communication techniques to provide voice
connectivity and allow mobility in the home and in metropolitan
area respectively. One technology aiming to provide an integrated
solution supporting voice and data wireless communications at
home is called HomeRF. It aims to interconnect personal computing
devices such as computers and PDAs, voice-enabled devices such
as cordless phones, and home entertainment systems such as DVD
players.
2. Technical Summary
HomeRF operates at
the 2.4 GHz Industrial, Scientific, and Medical (ISM) band. It
supports all CLASS features such as caller ID, call waiting, call
forwarding, and distinctive ringing allowing it to support standard
phone features that users are familiar with. HomeRF supports up
to 8 toll-quality voice connections, 8 priority-based multimedia
streams, and access to data at a rate of 10 Mb/s in version 1.0
of the standard and as high as 20 Mb/s in version 2.0 of the standard.
Transmission range is about 100 meters but can be extended at
the cost of the data rate. HomeRF also supports low power modes
and secure communications using 128 bit encryption against eavesdroppers
and denial of service attacks. Physical channel uses constant
envelope FSK modulation and utilizes frequency hopping spread
spectrum technique to minimize interference from other devices
such as cordless phones and microwaves. More specifically,
HomeRF supports 75 1 MHz channels each capable of 1.6 Mbps data
and voice throughput, and 15 5 MHz channels allowing 5 and 10
Mbps data sessions. MAC layer uses a combination of CSMA-like
contention resolution and priority-based reservation TDMA techniques.
This allows HomeRF to support Quality of Service policies, which
is important for multimedia applications. HomeRF 2.0 spec
extends 1.0 spec with features allowing easy roaming and connectivity
among data client devices. Specifically, methods for peer-to-peer
data transfers, and handoffs are specified.
3. Comparison with
similar technologies
Two major technologies
that compete with HomeRF are IEEE802.11 standard and Bluetooth
standard. The 802.11 outperforms HomeRF in terms throughput
and range but lags in the interference immunity property. Also,
it doesn't support CLASS features. Overall, 802.11
seems to better fit in the enterprise-type of networks. Bluetooth
supports easy formation of ad-hoc wireless "pico" networks
and has excellent interference immunity but has low data rate:
1 Mbps. Bluetooth, as well as 802.11, doesn't support CLASS
features. Bluetooth allows extremely low power consumption but
has short transmission range (about 10 meters). Bluetooth
was originally designed to replace cables and support short-range
data and voice communications between relatively small personal
devices such as headphones, and PDAs. Thus, HomeRF's features
make it a good choice for interconnecting wireless enabled devices
at home.