NATO Narrowband Waveform (NBWF) - overview of link layer design

This report is an updated and final version of a draft report distributed to the NC3B SC/6 AHWG/2 in September 2009. We have kept the same report number in order to avoid confusion. In coalition operations NATO has a need for a standardized, interoperable combat net radio waveform at VHF and UHF. Work is currently ongoing in NC3B SC/6 AHWG/2 to produce such a Narrowband Waveform (NBWF) standard. NC3A, CRC in Canada, FFI, and now also Kongsberg are taking part in this work. FFI has the responsibility for producing the link layer specification of the standard. The work has been going on since 2007 through the projects 1088 “TIPPER” and 1175 “Gjennomgående kommunikasjon for operative enheter”. This report presents a technical overview over the link layer design, and the considerations that underpin the design. It also adresses the impact of the requirements and the physical layer on the link design. In short, the link layer offers simultaneous voice and data services, where the channel capacity is exploited efficiently at any time. Multicast voice (Push-To-Talk) is the most important service, and the establishment of a multicast voice connection will pre-empt data traffic. When multicast voice is not activated in the network, the channel can be exploited efficiently to send data or unicast voice. All nodes in the network get a minimum dedicated channel access to send data or management information. Channel access to send data is based on contention where data with high priority will have the largest probability of accessing the channel. The link layer offers both a reliable and an unreliable packet data service for unicast connections and an unreliable service for multicast. FFI together with Kongsberg are now producing a final specification of the link layer in the form of a NATO STANAG. Simulations to validate the concept and tune parameters also remain to be done. In addition, a Head STANAG will be produced that describes the relationship between different parts of the NBWF (physical, link and network layers) and the interconnection with other networks.