Date: Mon, 4 Feb 2002 23:29:14 -0000 From: "Duncan Barclay" <dmlb@dmlb.org> To: "Vinod Namboodiri" <geekvinod@yahoo.com>, <freebsd-mobile@freebsd.org> Subject: Re: MAC layer Message-ID: <004401c1add3$c23d8180$27c8a8c0@my.domain> References: <20020204184715.29057.qmail@web21109.mail.yahoo.com>
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Hiya The MAC layer for most wireless standards ends up being implemented in the the device. The MAC can be implemented with software running on an embedded CPU, microcode running on a custom sequencer and in hardware (especially where real time event processing is required). Without access to the firmware source code and details of the chip set components it is unlikely that you can modify the MAC. The MAC implementation and programming details vary from manufacturer part to part. On some implementations it will be impossible to change without making a new IC. MAC protocols for wireless LAN are quite complex beasites. You can download the specification for 802.11 from the IEEE at www.ieee.org. This document defines the 802.11 MAC as used in 802.11, 802.11b and 802.11a devices (the difference between the different types is only in the physical layer - i.e. RF siganls, and a few timings in the MAC). You could also look at the Bluetooth specification at www.bluetooth.org - the Bluetooth MAC is very different to the 802.11 MAC. With 802.11, the MAC presents a means of sending packets of data from one node to another. The MAC defines how each node joins the network and how the nodes arbitrate for use of the RF to transmit a packet and its ack. The network basically uses a carrier sense, multiple access system where all nodes are (almost) peers. On the other hand, Bluetooth uses a different MAC where a node acting as the "master" will define when other "slave" nodes can use fixed timeslots. The 802 style MAC is very good for peer to peer networks carry asynchronous data. The Bluetooth approach is good at serving a number of users that want to send low latency isochronous data (e.g. voice). Other protocols, such as HomeRF, have merged the two together so that asynchronous and isochronous data can be dealt with efficently. FreeBSD network device drivers usually work above the MAC at the data link level and provide an interface to the network layers. Duncan ----- Original Message ----- From: "Vinod Namboodiri" <geekvinod@yahoo.com> To: <freebsd-mobile@freebsd.org> Sent: Monday, February 04, 2002 6:47 PM Subject: MAC layer > i am new into the wireless lan world.just started work > under a professor.our task was to set up a wireless > lan and then modify it to support mac layer > protocols.will be using orinoco gold cards and FreeBSD > 4.4 stable.Can anyone tell me how should i go about > making my own changes in the MAC layer once everything > is installed.should it be done on the FreeBSD source > code?I am a little confused right now.Hoping for some > conceptual advice. > Vinod > > __________________________________________________ > Do You Yahoo!? > Great stuff seeking new owners in Yahoo! Auctions! > http://auctions.yahoo.com > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-mobile" in the body of the message > > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-mobile" in the body of the message
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