In addition to efficient TDMA and automated bandwidth on demand (BoD), LINKWAY eliminates the need for additional third-party networking equipment. This results in improved overall network reliability, lowered costs, and simplified integration with terrestrial networks.

The LINKWAY platform incorporates enhanced features providing a unique architecture that supports mesh, star, virtual star, and hybrid topologies. The product’s inherent flexibility allows individual VSAT locations to be configured as very low-cost remote terminals and economical high-capacity gateways. LINKWAY broadband VSATs support multiple antenna and RF transceiver configurations with flexible carrier parameters that include variable bit-rates, power levels, and forward error correction (FEC) settings for each carrier.

    Every LINKWAY network has three basic parts:
     * The LINKWAY indoor unit (IDU)
     * The LINKWAY outdoor unit (ODU)
     * The heart of the LINKWAY network is the Network Control
        Center (NCC)—a  Sun workstation—which provides the
        management and control functions for all network terminals.

Figure1 illustrates a small network, with its NCC and NMS co-located with one of the LINKWAY IDU/ODU combinations, called a LINKWAY site.

Figure 1: A LINKWAY Network

    Broadband VSATs like LINKWAY are ideal for the current and emerging wideband multimedia applications en­countered by multinational corpora­tions, carriers, service providers, vir­tual private network operators, and Internet service providers (ISPs). An effective broadband VSAT platform must provide the following capabil­ities in order to address today’s diverse multimedia networking applications, which are discussed below:

·SUPPORT FOR A BROAD RANGE OF NETWORK
    TOPOLOGIES
    The three most popular and regularly encountered topologies include star (hub-and-spoke networks), mesh (any-to-any connectivity in one satellite hop), and virtual star or multi-star (hybrid networks with multiple hub locations). These are illustrated in Figure 2:

Figure- 2 LINKWAY—Three Topologies, One Platform

    A typical star network consists of a central hub location with many remotes supporting asymmetric outbound and in­bound traffic requirements. Applications include applica­tion–specific interactive sys­tems in banking, retail, and other industrial sectors; PSTN network extensions; broadcast services; and Internet network extensions.

    A mesh network consists of many terminals with one or two assigned to administer the network, no central hub location (although optional higher traffic gateways are possible), and support for any-to-any connectivity on one satellite hop. Applications include telemedicine, corporate wide-area voice and data communications, LAN extensions and videoconferencing.

A virtual star or hybrid network consists of two or more hubs or gateways and provides mesh connectivity between hubs, remote-to-mul­tiple hub connectivity, and asymmetric data rates. Virtual star networks are essentially two-tiered topologies support­ing high-traffic gateways with mesh connectivity to each other and small remote locations that are connected to the high-traffic gateways. Each tier requires links that provide fiber-like bit error ratio (BER) performance and asymmetric transmission rates. Typical applications include multinational corpor­ate intranets, and service pro­vider-operated virtual private networks.

    LINKWAY supports all three topologies, as well as:
     * Standard interfaces for pack­et-switched (IP, ATM, Frame Relay)
        and  circuit-switched (ISDN) networking ap­plications.
     * Broadband data rates between 312 ksps and 5 Msps.
     * Demand assigned allocation of bandwidth.

    LINKWAY is a powerful platform supporting high-rate, multiple protocol services for high-end applications, and affordable (small-aperture) remote terminals operating over low-rate carriers as well. The system operates seamlessly because larger VSAT sites can carrier-hop between large and small carriers as required by changing connectivity requirements.

    In a single-beam configuration, as illustrated in Figure3, the NCC links all of the traffic terminals in the network through the master reference terminal (MRT). (In Figuret 3, dotted lines indicate redundancy.)  In all cases, each LINKWAY terminal is capable of serving both as a reference and a traffic terminal. (The MRT, however, must reside at the same site as the NCC.)

    For instance, the MRT in Figure3 controls all geographic locations in the network. The NCC is co-located with the MRT, and both can be backed up by using an alternate master reference terminal (AMRT) and another NCC in a redundant configuration.

              Figure 3 : Single-Beam Configuration

    If the configuration is multiple-beam, as in Figure 4, there is also a supporting reference terminal (SRT) to control the traffic terminals associated with each satellite beam the MRT cannot see. The SRT relays NCC commands from the MRT.

            Figure 4 : Multiple-Beam Configuration

·SUPPORT FOR PACKET- AND CIRCUIT-SWITCHING
    PROTOCOLS
    Broadband VSATs need to provide native support for the most important and widely used packet-switching and circuit-switching protocols. This allows seamless transitions between the terrestrial and the satellite networks and  reduces or eliminates the need for additional third-party networking equipment. The LINKWAY indoor unit supports IP, ATM, and Frame Relay packet-switching protocols, and ISDN circuit-switching protocols.Legacy protocols, such as X.25 and SDLC, are supported over LINKWAY via a connected router using a standard LINKWAY interface.      * IP Service Features
     * ATM Service Features
     * Frame Relay Service Features
     * ISDN Service Features
     * Legacy Protocol Support
 

·FLEXIBLE CONNECTIVITY AND SATELLITE ACCESS         Broadband multimedia applications require flexible network architectures and a variety of satellite connectivity options. LINKWAY provides a multi-carrier (up to 256 carriers), multi-data-rate TDMA platform that can operate on one or more satellite transponders and supports flexible connectivity for any networking requirement.

    The TDMA burst modem within the VSAT platform operates at symbol rates between 312 ksps and 5 Msps to address a diverse range of broadband multimedia content. The transmit-and-receive data rates can be set independently for asymmetric transmission applications such as those typically encountered with IP applications. In addition, robust satellite links are possible with fiber-like BER performance since each carrier is assigned a convolutional-Viterbi inner code and a Reed-Solomon outer code.

LINKWAY is operable on any international or regional geosynchronous satellite system. Common frequency bands include C- and Ku-band; the system will also operate on bent-pipe Ka-band satellite systems.

·EFFICIENT DEMAND-ASSIGNED BANDWIDTH
    MANAGEMENT
    The LINKWAY system runs a central bandwidth management program in order to efficiently use space segment and provide high levels of end-user data throughput.

The bandwidth management function performs both fixed bandwidth allocation and dynamic bandwidth allocation (bandwidth on demand):
     * Fixed bandwidth allocation—Certain traffic categories in ATM
         and Frame Relay, and the circuit-switched nature of ISDN calls,
         require bandwidth to be allocated for the entire duration of
         the call. In these cases, bandwidth is allocated at call (or
         connection) setup and remains allocated for the entire duration of
         the call. The bandwidth is de-allocated when the call ends (or the
         connection is torn down).
     * Dynamic bandwidth allocation (bandwidth on demand)—
         Every LINKWAY terminal runs a Bandwidth Reporter program
         that continuously monitors the incoming user traffic.
         The dynamic bandwidth allocation function collects the
         reports from all traffic terminals and periodically runs
         an algorithm to distribute available bandwidth resources
         fairly and efficiently using three levels of fairness:
      * Outgoing Fairness—All connections originating from a
         particular terminal compete for the terminal’s total transmit
         capacity in a fair manner.
      * Incoming Fairness—All connections terminating at a particular
         terminal compete for the terminal’s total receive capacity in a fair
         manner.
      * System Fairness—All connections in the entire network compete
         for the total system capacity in a fair manner.

This algorithm provides bandwidth allocation in response to changing incoming user traffic rates in a dynamic manner.

  ·DIVERSE NETWORK APPLICATIONS
    LINKWAY is particularly well-suited to the diverse topologies needed for today’s wideband networks. Service providers and multinational corporations can economically establish mesh, star, or virtual star networks using a single platform.

Popular broadband VSAT network examples include:
     * Virtual private networks;
     * Private corporate networks;
     * Internet service providers;
     * Real-time digital video internetworking;
     * Wireless interconnectivity; and
* Disaster recovery.
 
·LINKWAY'S SUBSTANTIAL BENEFITS
    Networks based on LINKWAY products have clear advantages over the existing VSAT systems in the market. The benefits of LINKWAY networks include:
     * LINKWAY networks use a hub-less architecture;
     * Multi-protocol support enables easy migration to emerging
         applications;
     * LINKWAY networks support asymmetric traffic requirements;
     * LINKWAY networks support both full-mesh and star topologies
         on a single platform in a single hop;
     * LINKWAY’s unique patented dynamic bandwidth-on-demand
         (BoD) algorithm distributes network bandwidth among many sites
         effectively and efficiently as needed;
     * In situations where the wideband content is provided from various
         destinations, LINKWAY networks support multiple gateway
         network architectures without a hub; and
     * LINKWAY networks support multimedia applications through
         standard native ATM, Frame Relay, IP, and ISDN interfaces. 
         This enables LINKWAY terminals to interface seamlessly with
         existing terrestrial networks and to improve overall network
         reliability by minimizing the need for additional third-party devices.