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 | |
| 3 | The 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 |
| 4 | many Subscriber Stations '''(SS)''' forming a Star Topology. The BS broadcasts downlink and uplink maps periodically which tells a SS when would be |
| 5 | its 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 |
| 6 | i.e. no new SS`s are added to the system. Their is no notion of an ACK here and no contention issues. |
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. |
| 21 | For the Subscriber Station, the states look like the following: |
| 22 | |
| 23 | 1) 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 | |
| 25 | 2) The received packet was without errors, was a data packet, and the destination address matched the receiving node's self address |
| 26 | |
| 27 | 3) The received packet contained errors, was a data packet, and the destination address matched the receiving node's self address |
| 28 | |
| 29 | 4) The PHY receiver grabbed a packet off the channel and then tells the MAC to process it. This step is interrupt driven. |
| 30 | |
| 31 | |
| 32 | 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 three WARP node, |
| 33 | one BS and two SS. Any ethernet and higher layer traffic will be forwarded across the wireless medium. |