Internet Draft Stephen Bush Expires in June 1997 Sunil Jagannath <draft-bush-ncp-config-00.txt> ITTC January 16, 1997 Network Control Protocol for the Configuration of Mobile Wireless Beam- formed GPS-Based Networks Status of this Memo This document is a submission by the Information and Telecommunica- tions Technologies Center (ITTC) at the University of Kansas. Com- ments should be submitted to sbush@tisl.ukans.edu. Distribution of this memo is unlimited. This document is an Internet-Draft. Internet-Drafts are working doc- uments of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute work- ing documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference mate- rial or to cite them other than as ``work in progress.'' To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet- Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Abstract The Network Control Protocol (NCP) facilitates the configuration and rapid reconfiguration of mobile wireless beam-formed networks. It controls the operation of a network of omni-directional packet radios (orderwire) that overlays the mobile wireless network. Each network element in this network uses Global Positioning System (GPS) informa- tion to control a beamforming antenna subsystem which provides for spatial reuse. The GPS information is shared among the network ele- ments over the orderwire and an optimal topology for the beam-formed links is determined. Network Control Protocol Description Bush & Jagannath Expires in June 1997 [Page 1]
Internet-Draft Mobile GPS-Based Configuration 13 January 1997 Network Control Protocol Terminology This section defines some of the terminology used in the Description of the NCP operation. o "AX.25" Asynchronous X.25 Protocol (See [1]). o "Callsign" The packet radio callsign is assigned by the FCC and identifies the packet radio operator. o "Edge Switch" (ES) A node which either resides within the wireless network or at the edge of the fixed and wireless network and which serves as a base station. o "Global Positioning System" (GPS) Satellite system which provides location and time. o "Remote Node" (RN) A host with the ability to connect via a beamforming antenna to an edge switch (ES). Network Control Protocol Operation At the physical level we will be using the orderwire to exchange position, time and link quality information and to setup the wireless connections. The process of setting up the wireless connections involves setting up links between ESs and between ESs and RNs. The network will have one master ES, which will run a topology con- figuration algorithm and distribute the resulting topology informa- tion to all the connected ESs over point-to-point orderwire packet radio links. The point-to-point link layer for the orderwire uses AX.25 [1]. The master ES is initially the first active ES, and any ES has the capability of playing the role of the master. Bush & Jagannath Expires in June 1997 [Page 2]
Internet-Draft Mobile GPS-Based Configuration 13 January 1997 The first ES to become active initially broadcasts its callsign and start-up-time in a MYCALL packet, and listens for responses from any other ESs. In this prototype system, the packet radio callsign is assigned by the FCC and identifies the radio operator. Since it is the first active ES, there would be no responses in a given time period, say T. At the end of T seconds, the ES rebroadcasts its MYCALL packet and waits another T seconds. At the end of 2T seconds, if there are still no responses from other ESs, the ES assumes that it is the first ES active and takes on the role of the master. If the first two or more ESs start up within T seconds of each other, at the end of the interval T, the ESs compare the start-up times in all the received MYCALL packets and the ES with the oldest start-up time becomes the master. In this system, accurate time stamps are provided by the GPS. Each successive ES that becomes active initially broadcasts its call- sign in a MYCALL packet. The master on receipt of a MYCALL packet extracts the callsign of the source, establishes a point-to-point link to the new ES and sends it a NEWSWITCH packet. The new ES on receipt of the NEWSWITCH packet over a point-to-point orderwire link, obtains its position from its GPS receiver and sends its position to the master as a SWITCHPOS packet over the point-to-point orderwire link. On receipt of a SWITCHPOS packet, the master records the posi- tion of the new ES in its switch position table, which is a table of ES positions, and runs the topology configuration algorithm to deter- mine the best possible interconnection of all the ESs. The master then distributes the resulting information to all the ESs in the form of a TOPOLOGY packet over the point-to-point orderwire links. Each ES then uses this information to setup the inter-ES links as specified by the topology algorithm. The master also distributes a copy of its switch position table to all the ESs over the point-to-point order- wire links, which they can use in configuring RNs as discussed below. Also, the ES then uses the callsign information in the switch posi- tion table to setup any additional point-to-point orderwire packet radio links corresponding to the inter ES links required to exchange any link quality information. Thus this scheme results in a point-to- point star network of orderwire links with the master at the center of the star and also point-to-point orderwire links between those ESs that have a corresponding inter ES link. In the event of failure of the master node which can be detected by listening for the AX-25 messages generated on node failure, the remaining ESs exchange MYCALL packets, elect a new master node, and the network of ESs is reconfigured. Each RN that becomes active obtains its position from its GPS receiver and broadcasts its position as a USER_POS packet over the orderwire network. This packet is received by all the nearby ESs. Bush & Jagannath Expires in June 1997 [Page 3]
Internet-Draft Mobile GPS-Based Configuration 13 January 1997 Each candidate ES then computes the distance between the RN and all the candidate ESs which is possible since each ES has the positions of all the other ESs from the switch position table. An initial guess at the best ES to handle the RN is the closest ES. This ES then feeds the new RN's position information along with the positions of all its other connected RNs to a beamforming algorithm that returns the steering angles for each of the beams on the ES so that all the RNs can be configured. If the beamforming algorithm determines that a beam and TDMA time slot are available to support the new RN, the ES steers its beams so that all its connected RNs and the new RN are configured. It also records the new RN's position in its user posi- tion table which contains positions of connected RNs, establishes a point-to-point orderwire link to the new RN and sends it a HANDOFF packet with link setup information indicating that the RN is con- nected to it. If the new RN cannot be accommodated, the ES sends it a HANDOFF packet with the callsign of the next closest ES, to which the RN sends another USER_POS packet over a point-to-point orderwire link. This ES then uses the beamform algorithm to determine if it can handle the RN. This scheme uses feedback from the beamforming algorithm together with the distance information to configure the RN. It should be noted that the underlying AX.25 protocol [3] provides error free transmis- sions over point-to-point orderwire links. Also the point-to-point orderwire link can be established from either end and the handshake mechanism for setting up such a link is handled by AX.25. If the RN does not receive a HANDOFF packet within a given time it uses a retry mechanism to ensure successful broadcast of its USER_POS packet. A point-to-point orderwire link is retained as long as a RN is con- nected to a particular ES and a corresponding high-speed link exists between them to enable exchange of link quality information. The link can be torn down when the mobile RN migrates to another ES in case of a hand-off. Thus at the end of this network configuration process, three overlaid networks are setup, namely, an orderwire network, an RN to ES network and an inter-ES network. The orderwire network has links between the master ES and every other active ES in a star con- figuration, links between ESs connected by inter-ES links as well as links between RNs and the ESs to which they are connected. Raw pipes for the user data links between RNs and appropriate ESs as well as for the user data links between ESs are also set up. Finally, see [2] and [3] for the definition of managed objects for the NCP and Virtual Network Configuration (VNC). Network Control Protocol Packet Types Bush & Jagannath Expires in June 1997 [Page 4]
Internet-Draft Mobile GPS-Based Configuration 13 January 1997 The network control protocol uses the following packet types shown below. ----------------------------------------------------------------------- |MYCALL | Callsign, Boot-Time | ----------------------------------------------------------------------- |NEWSWITCH | empty packet | ----------------------------------------------------------------------- |SWITCHPOS | GPS Time, GPS Position | ----------------------------------------------------------------------- |TOPOLOGY | Callsign and Position of each node with inter-connections | ----------------------------------------------------------------------- |USER_POS | Callsign, GPS Time, GPS Position | ----------------------------------------------------------------------- |HANDOFF | Frequency, Time Slot, ES GPS Position | ----------------------------------------------------------------------- The MYCALL packet contains the ES identifier (packet radio Callsign) and the time it powered-up. The NEWSWITCH packet is an empty packet which serves as an acknowl- edgment and completes the handshake between the ES and RN. The SWITCHPOS packet contains the current ES time and location. The TOPOLOGY packet contains packet radio callsigns and positions of all nodes and the beamformed links to be established between them. The USER_POS packet contains the callsign, current time, and position of an RN. The HANDOFF packet contains the frequency, time slot, and ES posi- tion. It is sent by an ES to a RN indicating handoff to this ES. Security Considerations All orderwire packets are DES encrypted. References [1] AX.25 Amateur Packet Radio Link-Layer Protocol, IEEE October (1984). Bush & Jagannath Expires in June 1997 [Page 5]
Internet-Draft Mobile GPS-Based Configuration 13 January 1997 [2] The Definition of Managed Objects for the Configuration of Mobile Wireless Beamformed GPS-Based Networks, draft-bush-rdrn- mib-00.txt, Stephen F. Bush, Sunil Jagannath. [3] The Definition of Managed Objects for Virtual Network Configura- tion, draft-bush-vnc-mib-00.txt, Stephen F. Bush, Sunil Jagannath. Author's Address Stephen F. Bush Sunil Jagannath Information and Telecommunications Technologies Center (ITTC) University of Kansas Lawrence, Kansas 66045 Phone: (913) 864-7761 EMail: sbush@tisl.ukans.edu Bush & Jagannath Expires in June 1997 [Page 6]