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I have been a Spread Spectrum person from way back - having first become
interested in the subject back when I was doing my degree at University in
the early 1990's. Back then Spread Spectrum was just starting to emerge,
with the 2 mBits WaveLan card available if you could afford it. Regardless
of the cost I saw that Spread Spectrum was going to emerge eventually as a
powerhouse of modern technology.
For my thesis I looked at some of the issues involved in a Half Duplex
Spread Spectrum radio network, and worked out that if these issues could be
solved, then half duplex was the way to go in a large distributed network.
So here we are a few years later, and the IEEE have come up with a standard
they have called 802.11 which is taking the world by storm thanks to the
ease of interfacing, low cost and high bit rates. A lot of us have used
wireless networks, but how many of them know what goes on behind the scenes?
I spent about six months searching for books on the internals of 802.11 and
found myself buying book after book for a scant chapter on the protocol. In
most cases the book was saying just what I already knew, usually looking at
the physical layer, and ignoring the upper layers.
Until I started reading this book I did not know much at all about the
underlying technology. After reading this book I realised that I knew a huge
amount about the underlying technology of 802.11, and at the same time I
knew very little.
I should say at the outset that I have not looked past the first 150 pages
of this book - the other 300 pages look interesting, but are looking more at
issues such as the physical layer, and implementation.
The biggest thing that this book taught me was how similar AX25 Packet Radio
and 802.11 Wireless Ethernet are. After all, 802.11 is basically just a
version of AX25 on steroids, optimised and expanded. The heritage is obvious
when you start looking at the details - In 802.11 a base station callsign is
called and SSID. In AX25 the SSID is the numeric identifier at the end of
the callsign.
The book goes into great detail describing all the fields of the various
packet formats, as well as all the timers that are built into the system.
The reader is left with the impression that a lot of thought has gone into
the design of the protocol, and that a lot of effort has gone into how to
present this information to the reader.
I suspect that you would have problems using this book to implement the link
layer of 802.11, but that really isn't the purpose of this book - it is more
to explain the details. I have used this book to analyse the performance of
802.11 when the distance between two stations is increased beyond what would
normally be considered the logical limit.
In this case I found that most of the information I needed was detailed or
could be inferred from the book. This makes the book far better than any
other book on the subject that I have found.
This book is full of hidden Gems such as the seven page chapter on
performance tuning. The table included in this book detailing the tunable
parameters not only lists what the parameter does, but also what happens
when you increase it and decrease it.
One novel section of the book deals with using the Etherial software to
listen to the packets being broadcast over air. This is extremely useful to
anyone attempting to debug a wireless installation.
On the minus side I have found that there are about 100 pages devoted to
specific hardware that limiting the life of this book - although I must
admit that the concepts introduced in these sections are likely to outlive
the actual products.
My copy of this book was purchased from OpAmp Technical Bookstore in
Hollywood, Ca. People wanting to buy a copy of this book mail order are
encouraged to purchase one from AMAZON.CON by clicking
here
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