Patent Application: US-11543598-A

Abstract:
the invention provides a method for communication between a plurality of stations in a communication network using media access protocol , in which medium access is granted to stations obtaining a successful reservation of the medium and in which data transmission verification is performed by the protocol within the reservation . in the method a station sends a request message on the communication medium for a reservation of the medium to a recipient station in the network . the recipient station sends a reservation confirmation message back to the sending station which receives it and responds to the reservation confirmation message by sending an ordered sequence of data frames to the recipient station . after sending the ordered sequence of data frames the sending station sends an end of transmission message to the recipient station , which replies by sending back an end of transmission confirmation identifying the number of frames received in their original sequence . if the number is not correct remedial action can be taken by the sending station to resend missing data . address conflict resolution is also provided by another aspect of the invention . the invention has embodiments which handle unicast and groupcasting transmissions .

Description:
in this section we will describe the methods of the invention using a distributed csma / ca type of mac protocol with repetition coding as described in the background . the invention contains several new frame types , control frames , header and mac body fields as illustrated in detail in fig2 . three new frame types were invented to compliment the mac protocol , namely the sequenced data frame ( sdata ), sequenced poll frame ( spoll ) and the sequenced acknowledgment ( sack ) frame . the sdata frame has a new sequence field which has been added to the mac body of the frame . the spoll frame is a simple header with a remote unicast destination address ( da ) field contained in the mac body . the sack frame is a simple header with the remote unicast source address ( sa ) which should be identical to the ( da ) field of the spoll contained in the mac body . the spoll is used to poll remote stations to identify whether the data previously sent was received successfully in sequence . the sack frame provides the target stations response to the poll . the eobc header was also modified to add a new sequence ( seq ) field to provide a means for the target station to feedback status for previously transmitted data frames received successfully in sequence without error . the basis for the invention is to provide a sequencing feature for data frames sent at the mac level to reduce the dependency on link layer polling . frames which are successfully received in sequence will be acknowledged immediately to the upper link layer and will not require a polling sequence . in networks that incur high latency this is a valuable savings . even networks that do not incur a high latency will still realize some performance gains . in this process , illustrated in fig3 a station ( a ) would contend for the channel using the previously defined rts / cts process . the destination field in the mac body of the rts frame from ( a ) is required to be a unicast address directed at a specific target station ( b ) as this process is only applicable for a burst of data between 2 stations . upon reception of the cts from ( b ) the requesting station ( a ) will begin sending the sequenced data ( sdata ) frames to ( b ). the sdata frames sent to ( b ) are required to use a unicast address field for the destination address ( da ) in the mac body . each consecutive sdata frame within the reservation burst will provide an incrementing number in the seq field of the mac body . after the last sdata frame is transmitted then ( a ) will begin termination of the reservation using an eob frame . upon reception of the eob frame ( b ) will return to ( a ) an eobc to complete the termination handshake . the eobc returned from ( b ) to ( a ) will contain a new seq field which will indicate the number of frames received successfully in their original sequence during the reservation burst . the seq counter on both stations will be reset at the end of the reservation . the sequence counter could start at any known position , the typical value used would be zero or one . if a station ( a ) were to send 4 frames to station ( b ) upon terminating the reservation the target station would inform the requesting station of the next frame expected in sequence . if a frame was received out of sequence the target station ( b ) would stop incrementing it &# 39 ; s sequence counter and tell the requesting station ( a ) to retransmit at the point data was received out of order from it &# 39 ; s original sequence . the requesting station ( a ) can pass this information to the link layer user of the mac . if the user of the mac is informed all data frames were received correctly it will no longer be required to poll the remote station to discover this information . the polling requirement would now only be necessary in cases where the eobc frame was lost . two possible outcomes can happen at station ( a ). if the eobc frame was received by ( a ) then the link layer will know immediately which frames were lost and can begin error recovery immediately . however , if the eobc frame was lost then the link layer will not know which frames were successfully received and a polling sequence would know be required . this complete process will result in a valuable reduction in link layer overhead and reduce the amount of time the station would spend contending for the media . link control begins error recovery for lost data if any encountered many networking protocols use the concept of group addressing or multicast addressing schemes . the basic principal is that you provide a unique address shared by multiple stations . when data is sent to the group address all stations listening on the group address will receive the data . the main motivation behind this style of addressing process is it allows a single transmit request to be heard by multiple stations simultaneously . however , in wireless protocol schemes you are often not sure whether all the target stations can all hear the transmitting source device . the basic idea with groupcasting is to provide a reliable transfer mode with group addressing ( multicast ) by providing confirmation that the data was actually successfully received in its original sequence . the fact that this is all performed at the mac level provides additional performance ( measured in terms of throughput ) advantages that could not be achieved by using this process at an upper protocol layer . the groupcasting transfer mode is similar to the sequenced data transfer mode except for the fact that the transmission now involves multiple intended receivers . in this process , as illustrated in fig4 the source station ( a ) will contend for and reserve the medium with a target station ( b ). the target station ( b ) may be optionally part of the group . when the media has been reserved ( a ) will send a burst of sdata frames using a multicast ( group ) destination address ( da ). in this scenario , it is expected that ( b ) would be a member of the group listening on the group address . we send 4 sequenced data frames , as described in the previous process the seq parameter is incremented for each consecutive sdata frame . when the requesting station ( a ) has finished transmitting the sequence of sdata frames it will then proceed to individually poll each member of the group . the requesting station could also optionally select to only poll a select subset of the group . a group registration procedure would need to be defined to enable the source station ( a ) to know all remote stations associated to the specific group address . ( a ) will then proceed to poll each individual member of the group . the polling procedure is completed by ( a ) sending an spoll frame to a target station identified by the unicast ( da ) in the mac body . the target station at which the spoll frame was directed will reply with a sack frame . the header of the sack frame will provide the seq field from the target station and will identify the next frame expected in sequence to be received by the target station in this reservation burst . the body of the sack frame will include the ( sa ) field for the responding station and will be identical to the ( da ) provided in the spoll frame . a timeout facility has been incorporated on the requesting station ( a ) to handle the case where the sack response from ( b ) may get lost and not be received at ( a ). in such cases ( a ) could attempt to retransmit the spoll frame within the reservation and repeat the previously described procedures . a retry limit would be defined to control the number of times ( a ) would be allowed to attempt to get a response to the spoll . the spoll and sack exchange between ( a ) and the next target device would then be repeated for every unicast ( da ) address included in the group . when all target devices in the group has been polled the source station ( a ) will then terminate the reservation by using the eob / eobc handshake termination . the requesting station ( a ) also has the optional facility of polling the target station ( b ) explicitly to receive the seq results or it may rely on the seq field in the eobc frame . providing the seq field on the eobc would eliminate the need of polling the station used to establish the reservation . after all stations have been polled and the reservation has been terminated the mac will report to the upper link layer the status of the transmitted data . if all stations received the intended data then no other actions are required at the link layer . however , if data loss was detected then the link layer can perform it &# 39 ; s error recovery procedures . in the example shown in fig4 you can see a situation where station ( a ) and ( c ) received all 4 frames correctly in their original sequence . however , station ( b ) only received the first 2 frames correctly . the link layer can now use this information & amp ; when performing link layer recovery . repeat poll loop for each member until all spoll frames transmitted inform link control number frames received in sequence by the group link control begins error recovery for lost data if any encountered all mac layer protocols use some form of addressing process to uniquely identify each station . typically a link protocol would be responsible for identifying address collisions and taking procedures to resolve them . the benefits of this new invention is the mac will be able to detect and resolve the address conflict quicker and easier than upper layer link control protocols . also , the mac protocol will provide a local mapping of the mac address to isolate the dynamic process from the upper layer protocol . this will allow the mac to reassign a new mac address with no involvement required by the upperlayer link protocol . in this process , this aspect of the invention would involve the mac protocol assuming the responsibility for address conflict resolution . the source station will listen to all received mac frames which are using a ( sa ) field . examples of these frames would include all types of data frames and the sack frame . if a ( sa ) is detected with a matching value and the frame is received without errors ( ie no crc error detected ) then the conflict is detected and reported . the mac protocol performs this check on every frame received carrying an ( sa ). upon detection the mac will reassign a new value for it &# 39 ; s own mac address and update the address mapping table . the mac station would also need to inform all stations it was in communication with of it &# 39 ; s new address . the process could also be applied to resolve duplicate addresses on behalf of other stations in the network . this would be accomplished using the address mapping table with link control and mac address pairings . a received mac address paired with an lc address different than identified in the address table would be used to identify the owning station of the conflict . in the preceding description pseudocode examples have been provided for a more thorough understanding of described embodiments of the invention . various applications of the pseudocode will be evident to those skilled in the art , as depending on the objectives and equipment used for communications network stations the pseudocode could be used for the basis of software , micro code or hardware implementation . 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