Changes between Version 1 and Version 2 of WANMAC


Ignore:
Timestamp:
Jul 11, 2006, 5:28:35 PM (18 years ago)
Author:
varunnayyar
Comment:

--

Legend:

Unmodified
Added
Removed
Modified

  • WANMAC

    v1 v2  
    11= Description =
    2 The ACKMAC is a modified ALOHA MAC that serves as the framework for all other MACs. In this scheme, nodes have no knowledge of any other nodes; there is no carrier sensing (CSMA/CA), and there is no request-to-send/clear-to-send (RTS/CTS). Instead, nodes transmit whenever they have information to transmit, and only move on to the next packet once the original transmit is acknowledged (ACKed). If no ACK is received, a collision is inferred and the packet is re-transmitted.
     2
     3The WANMAC is a TDM MAC that serves as a framework for all '''Scheduled Access''' MACs. In this scheme, their is one Base Station '''(BS)''' and
     4many Subscriber Stations '''(SS)''' forming a Star Topology. The BS broadcasts downlink and uplink maps periodically which tells a SS when would be
     5its turn to send and receive data, as is done in 802.16 or Wimax.  For the first implementation we have assumed the system to be in equilbrium
     6i.e. no new SS`s are added to the system. Their is no notion of an ACK here and no contention issues.
    37
    48[[Image(MACstates.jpg, align=right, 400)]]
    59
    6 This behavioral description can be transformed to a state-machine, which in turn can be transformed to C-code. A few typical transitions through states are numbered.
     10This behavioral description of both BS and SS can be transformed to state-machines, which in turn can be transformed to C-code. A few typical
     11transitions through states are numbered. For the Base Station, we have the following states:
    712
    8131) The received packet was without errors (CRC passed), was an ACK packet (as opposed to a data packet), and the destination address matched the receiving node's self address
    … …  
    14194) The PHY receiver grabbed a packet off the channel and then tells the MAC to process it. This step is interrupt driven.
    1520
    16 The behavior described above is a small subset of that which is implemented in the attached code. Here, we bridge that state machine to a source and a sink (ethernet and OFDM physical layer respectively for a transmitter, and vice versa for a receiver). In that way, we have a project that creates a virtual wire between two WARP nodes. Any ethernet and higher layer traffic will be forwarded across the wireless medium.
     21For the Subscriber Station, the states look like the following:
     22
     231) The received packet was without errors (CRC passed), was an ACK packet (as opposed to a data packet), and the destination address matched the receiving node's self address
     24
     252) The received packet was without errors, was a data packet, and the destination address matched the receiving node's self address
     26
     273) The received packet contained errors, was a data packet, and the destination address matched the receiving node's self address
     28
     294) The PHY receiver grabbed a packet off the channel and then tells the MAC to process it. This step is interrupt driven.
     30
     31
     32The behavior described above is a small subset of that which is implemented in the attached code. Here, we bridge that state machine to a source and a sink (ethernet and OFDM physical layer respectively for a transmitter, and vice versa for a receiver). In that way, we have a project that creates a virtual wire between three WARP node,
     33one BS and two SS. Any ethernet and higher layer traffic will be forwarded across the wireless medium.
    1734
    1835