KR19990022705A - High speed and efficient packet transmission system and method - Google Patents

Abstract

To achieve maximum efficiency and minimum delay in digital communication networks, packets may be transmitted and transmitted through digital communication networks 101, 102, 103, 104, 105 and 106, utilizing both variable length packets and fixed length packets or cells. A high speed and efficient packet transmission system and method for routing is disclosed. Network efficiency is maximized by using variable length packets to transmit information across transmission line 102 and network speed is maximized by delivering information to the intended destination using a cell.

Description

High speed and efficient packet transmission system and method

In a packet switching network, the information is delivered in packets, each of which contains some control information in some (or all in the case of short messages) of the subscriber's information. At a minimum, the control information includes the destination address of the packet to enable the network to send the packet over the network and deliver it to the intended destination. As a route, a packet is received at each node, stored roughly and passed to the next node.

In a packet switched network, network resources are shared by multiple subscribers as needed. In other words, a packet is transmitted when it becomes available, and if there is nothing to send, no transmission facility is occupied by the source. Connections between subscribers are logical rather than physical. The basic advantage of such a switching network is that it optimally uses network resources because the required physical channels are never idle except when there is no call.

In addition, since packet switching operates in a burst-oriented access mode, a single network resource can accommodate multiple subscribers that transmit and receive information at different or variable data rates. The ability to simultaneously accommodate variable rate information from multiple subscribers allows a packet switching network to achieve maximum bandwidth efficiency. Since the length of the variable length packet is directly proportional to the rate of information to be transmitted within a given time period, the variable length packet contains the minimum number of idle bits. This allows variable length packets to utilize the bandwidth capacity of the transmission medium at maximum efficiency.

However, many of the advantages of variable length packet switching are costly. As a result of the overhead involved in storing and processing control information, variable length packets delay time and introduce other overhead inefficiencies during dispatch that do not meet the low latency requirements of certain types of information, such as voice communications.

In order to reduce the delay time involved in processing the control information, fixed length packets or cells (cells are defined as one packet having a fixed size) can be used to send information over the network. There are two advantages to using cells as compared to using variable length packets to send information. First, the cells simplify network routing and / or switch design because of the synchronized flow of cells from all inputs through the switch element. Secondly, the cell reduces the processing of control information at the network node because it does not require cell length calculation. These two advantages allow the cells to be sent and sent over the communication network with a minimum delay that makes the cells particularly suitable for low-delay communications such as voice communication. Asynchronous Transfer Mode (ATM) has become the cited standard for cell arrays. ATM is a low-delay, high-bandwidth, fixed cell size, packet switching and multiplexing technique.

However, using a cell involves one obvious disadvantage. In the case of a communication system that receives and transmits variable rate information, such as voice information, the cells do not exhibit the bandwidth effect achieved by variable length packets. The length of the variable length packet varies in proportion to the rate of variable rate information. Thus, when using variable length packets, there is a minimum number of idle bits for each packet. In contrast, each cell must be long enough to accommodate the fastest variable rate of information. Thus, later rate information occupies only a portion of the available bit space on a fixed length cell and the rest of the cell consists of idle bits or filler bits.

Therefore, there must be a balance between network efficiency and network speed. Although variable length packets can maximize network efficiency, they exhibit greater switching and routing delays than those represented by cells. Conversely, fixed length cells can be switched and routed faster than variable length packets but are less efficient because they contain a large number of idle bits.

Network efficiency is of utmost importance in the telecom industry because its ability to handle more subscribers at the same time as responding to network efficiency equals more tax revenues to customers. On the other hand, the quality of transmission is very important to the customer. Therefore, minimizing transmission delay is very important in the telecommunications industry.

With these two competing concerns in mind, there is a clear need for a digital communications network that optimizes transmission efficiency and optimizes transmission latency.

Summary of the Invention

The present invention is a novel packet transmission system and method for transmitting packets over a digital communication network. Packet transmission systems use both variable length packets and fixed length packets, or cells, to optimally obtain maximum efficiency and minimum delay during the transmission of information over a digital communication network. Network efficiency is maximized using variable length packets when information is transmitted over the transmission line. Network delay is minimized by converting variable length packets into cells at the switch or router interface and forwarding the cells to their appropriate destination port according to each cell's destination address.

The present invention can operate in two modes to provide two-way communication between end subscribers. These two modes are referred to as the forward link and the reverse link. The subscriber information signal on the reverse link is received by the first signal processor, transmitted by the system, and then transmitted by the second signal processor to the next destination location. On the forward link, the subscriber information signal is received by the second signal processor, passed through the system, and sent by the first signal processor to the next destination location.

In one embodiment of the invention, the first signal processor on the reverse link receives the subscriber information signal and processes it in a variable length packet format. The variable length packet is transmitted via a transmission line to a first packet converter which converts the variable length packet into a cell. Cells are forwarded by a system router that forwards each cell to a specific destination port according to the destination address of each cell. These cells are transferred directly to an asynchronous transmission mode (ATM) network or another network capable of receiving the cell, or forwarded back to the first packet converter in the forward link direction (see forward link below) or to the second packet converter. Delivered. In the second packet converter, the cells are converted back to variable length packets. The variable length packet is processed by the second signal processor in the next transmission format and sent to the next destination.

On the forward link, the second signal processor receives and processes the subscriber information signal to produce a variable length packet. The variable length packet is converted into a cell by a second packet converter. The cells are delivered to the first packet converter by the system router. In the first packet converter, the cells are converted back into variable length packets. These variable length packets are sent along the transmission line to the first signal processor for processing in the next transmission format and to the next destination.

The system router may receive the cells directly from an Asynchronous Network (ATM) network or other fixed length packet source. These cells may be delivered to the next destination in either the forward or reverse link direction. As mentioned above, the system router can send cells directly to ATM networks or other networks capable of receiving information signals in fixed length packet (cell) formats.

The present invention relates to the field of digital communications. In particular, the present invention relates to a system and method for packet transmission and transmission in digital communications utilizing both variable length packets and fixed length packets to obtain optimal efficiency and speed over a network.

The features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the drawings.

1 is a schematic diagram of a typical packet transmission system,

2 is a schematic diagram of a typical code division multiple access (CDMA) packet transmission system.

An exemplary packet transmission system in which the present invention is implemented is illustrated in FIG. The packet transmission system operates in two modes to provide bidirectional communication between end subscribers. These two modes are referred to as the forward link and the reverse link. On the reverse link, the subscriber information signal is received by the first signal processor and passed through the system and sent by the second signal processor to the next destination. On the forward link, the subscriber information signal is received by the second signal processor and transmitted through the system and transmitted by the first signal processor to the next destination.

On the reverse link, the first signal processors 101a-101n receive subscriber information signals and process them in a variable length packet format. The variable length packet format is one of various formats known in the art (HDLC, LAPB, LAPD, etc.). Variable length packets are transmitted via transmission lines 102a-102n. These transmission lines are typically E1 or T1, which are commercial lines with standard bandwidth. However, other types of lines may be used depending on the capacity requirements of the particular system. Variable length packets utilize the maximum bandwidth capacity of the transmission line since such packets contain a minimum number of idle bits. Thus, more users can send information through the line at the same time and line efficiency is maximized.

With completion of this pass on transmission lines 102a-102n, variable length packets are converted into fixed length packets, or cells, by first packet converters 103a-103n. In contrast to variable length packets, delivery of cells does not require time consuming packet length operations. Thus, switching and routing is accomplished using cells that can be switched or forwarded faster than variable length packets. After the variable length packet is converted into cells, the system router 104 forwards each cell to the appropriate destination port according to the destination address of each cell.

Standard packet switches and routers are relatively inexpensive and do not exhibit inherent bandwidth limitations in the transmission line. Thus, gaining bandwidth efficiency in a switch or router is a relatively less concern when compared to obtaining the low latency requirements of many forms of communication. In addition, transmission lines are leased from local telephone carriers at significant cost to ensure that they are utilized to their full capacity to achieve cost efficiency. System routers, on the other hand, are generally not leased. If one system router cannot handle the amount of information calls in the area, it can be upgraded or a second router can be built at a relatively low long-term cost to handle additional information communication. Thus, achieving bandwidth efficiency in a system router is not as important as obtaining bandwidth efficiency over leased transmission lines. The main concern for system routers is to deliver information to the appropriate destination with minimal delay.

The cells may be either asynchronous transmission mode (ATM) network or one of the other networks capable of receiving the cell either directly, or the first packet converter 103a-103n (see section on forward link below) or the second packet converter ( 105a-105m). The second packet converters 105a-105m convert the cell back into variable length packets. The variable length packet is processed by the second signal processor 106a-106n in the next transmission format and sent to the next destination.

On the forward link, second signal processors 106a-106n receive subscriber information signals and process them in variable length packet format. Variable length packets are converted into cells by second packet converters 105a-105m. The cells are delivered by the system router 104 to the first packet converters 103a-103n according to the destination address of each cell. The first packet converters 103a-103m convert the cells back into variable length packets. The variable length packet is transmitted through transmission lines 102a-102n to first signal processors 101a-101n which are processed in the next transmission format and are sent to the next destination.

The system router 104 receives the cell directly from an Asynchronous Network (ATM) network or other fixed length packet source. These cells may be delivered in either forward link or reverse link directions to the next destination. As mentioned above, the system router may send the cell directly to an ATM network or another network capable of receiving information signals in fixed length packet format.

A typical code division multiple access (CDMA) packet transfer system in which the present invention is implemented is illustrated in FIG. The use of CDMA modulation technology is one of various techniques to facilitate communication when there are a large number of system subscribers. The use of CDMA technology in multiple access communication systems is disclosed in US Pat. No. 4,901,307, named Spread Spectrum Multiple Access Communication System using satellite or terrestrial repeaters and assigned to the assignee of the present invention. This disclosure is incorporated herein by reference.

The relevant features of the CDMA packet transfer system (known as the CDMA Cellular Landbase Network (CCLN)) are shown in FIG. The CDMA packet transmission system consists of two parts: a plurality of base station transceiver subsystems (BTSs) 201a-201n and a single base station controller (BSC) 200. In a CDMA communication system, CDMA variable length packets are transmitted over the air between the subscriber and base station transceiver subsystems 201a-201n. Base station transceiver subsystems 201a-201n are links between a subscriber and base station controller 200 and provide a common air interface to the subscriber. The base station controller 200 includes resources for establishing and maintaining a communication channel and communicating information between the base station transceiver subsystems 201a-201n and other networks, such as a public switched telephone network (PSN).

The CDMA packet transmission system operates in two modes to provide bidirectional communication between end subscribers. These two modes are referred to as the forward link and the reverse link. On the reverse link, subscriber information signals are received by base station transceiver subsystems 201a-201n, routed through base station controller 200, and transmitted by selector bank subsystem (SBS) to their next destination. On the forward link, subscriber information signals are received by selector bank subsystems 206a-206n, passed through base station controller 200, and transmitted by base station transceiver subsystems 201a-201n to the next destination.

On the reverse link, base station transceiver subsystems 201a-201n receive incoming CDMA signals and process them into High-level Data Link Control (HDLC) variable length packets. The HDLC format is a flag synchronous transmission control format in which information having an arbitrary bit length is treated as a transmission unit (sometimes called a frame) called a variable length packet. The HDLC format enables the transmission of continuous information in variable length packets. After base station transceiver subsystems 201a-201n process the incoming CDMA signal, the resulting HDLC variable length packets are forwarded to base station controller 200 via transmission lines 202a-202n. At base station controller 200, HDLC packets are received by first packet converters 203a-203m that convert HDLC variable length packets into asynchronous transfer mode (ATM) cells. ATM is a low latency, high bandwidth, fixed packet size, packet switching, and multiplexing technique that becomes an accepted standard for cell delay. After the first packet converters 203a-203m convert the HDLC packets into ATM cells, the ATM cells are routed by the system packet routers to their appropriate destination ports according to each cell's destination address. The ATM cell may be passed back to the first packet converters 203a-203m in the forward link direction to the ATM network or to one of the second packet converters 205a-205m. In the second packet converters 205a-205m, the ATM cells are converted back to HDLC variable length packets. HDLC packets are sent to selector bank subsystems 206a-206n, which process the HDLC packets in their transmission format and send them to the next destination.

The selector bank subsystems 206a-206n are responsible for the call processing request of the base station controller 200 and provide an interface between the base station controller 200 and other networks (PSTN), such as a public switched telephone network (PSTN). Typically, the HDLC packet will contain voice information and the selector bank subsystem processes the HDLC packet as a pulse code modulation (PCM) voice signal that is time division multiplexed and sent to a public switched network. Each selector bank subsystem 206a-206n uses a time division multiplexing technique for individual subscriber information signals transmitted between the selector bank subsystems 206a-206n and a public switched telephone network or other interfacing network. It includes a plurality of selector elements that provide resources for allocating channels. Public switched telephone networks are always local telephone carriers. In addition to voice communications, selector bank subsystems 206a-206n process other types of data for various networks and interfaces.

On the forward link, selector bank subsystems 206a-206n receive subscriber information signals such that each subscriber signal is provided with its own transport channel between the selector bank subsystem and a public switch telephone network or other interfacing network. Time division multiplex the signals. Typically, subscriber information signals will be pulse code modulation (PCM) voice communications transmitted by public switched telephone networks. However, other types of signals may be received and processed by the selector bank subsystems 206a-206n to enable interfacing with various networks. The selector bank subsystems 206a-206n process the subscriber information signal into HDLC variable length packets. HDLC packets are sent to second packet converters 205a-205m, which convert HDLC packets into ATM cells. ATM cells are forwarded by the system router 204 to the appropriate destination port according to the destination address of each cell. After the ATM cell is routed, the cells are converted back to HDLC variable length packets by the first packet converters 203a-203m. HDLC packets are sent to base station transceiver subsystems 201a-201n via transmission lines 202a-202n. Base station transceiver subsystems 201a-201n treat the variable length packets as CDMA signals and send them to the next destination.

The system router 204 may bypass the selector bank subsystems 206a-206n and the second packet converters 205a-205n to receive ATM cells directly from the ATM network. At system router 204, the ATM cell may be delivered to the next destination either on the forward link or the reverse link.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of inventive capabilities. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features described herein.

Claims (24)

A first signal processor for processing the received subscriber information signal into a variable length packet and processing the variable length packet into an output subscriber information signal; A transmission line connected to the first signal processor; A first packet converter connected to said transmission line for converting said variable length packet into a cell and converting cells into a variable length packet; And A system router connected to said first packet converter, said system router for delivering said cells to their next destination. The method of claim 1, A second packet converter connected to the system router for converting cells into variable length packets and converting variable length packets into cells; And And a second signal processor coupled to said second packet converter, for processing a variable length packet in a next transmission format and for processing a received subscriber information signal into a variable length packet. 3. The packet transmission system of claim 2, wherein the variable length packet is a high-level data link control variable length packet. 4. The packet transmission system of claim 3, wherein the cell is an asynchronous transmission mode cell. 3. The packet transmission system of claim 2, wherein the cell is an asynchronous transmission mode cell. 2. The packet transmission system of claim 1, wherein the first signal processor includes a base station transceiver subsystem, wherein the subscriber information signal received and transmitted by the first signal processor is a code division multiple access spread spectrum signal. . 3. The packet transmission system of claim 2, wherein the first signal processor includes a base station transceiver subsystem, wherein the subscriber information signal received and transmitted by the first signal processor is a code division multiple access spread spectrum signal. . 8. The method of claim 7, wherein the second signal processor includes a selector bank subsystem, wherein the subscriber information signal received and transmitted by the second signal processor is a pulse-code-modulated, time-division-multiplexed signal. Packet transmission system. 3. The method of claim 2, wherein the second signal processor includes a selector bank subsystem, wherein the subscriber information signal received and transmitted by the second signal processor is a pulse-code-modulated, time-division-multiplexed signal. Packet transmission system. A base station transceiver subsystem further comprising a CMDA signal processor for transmitting and receiving CDMA signals to and from a plurality of system subscribers, processing the received CDMA signals into variable length packets and processing the variable length packets into output CDMA signals; A transmission line connected to the base station transceiver subsystem; A first packet converter connected to said transmission line, for converting a variable length packet into a cell and converting a cell into a variable length packet; A system router connected to the first packet converter, for routing the cell; A second packet converter connected to said system router for converting said cell into a variable length packet and converting a variable length packet into a cell; And A selector bank subsystem connected to the second packet converter, The selector bank subsystem is A signal processor for processing the variable length packet in the following transmission format and processing the received subscriber information signal as a variable length packet; And A code division multiple access packet transmission system comprising a plurality of selector elements each providing a unique transport channel using time division multiplexing (TDM) for each individual subscriber information signal. 11. The system of claim 10, wherein the variable length packet is a high-level data link control variable length packet. 12. The system of claim 11, wherein the cell is an asynchronous transmission mode cell. 12. The system of claim 10, wherein the cell is an asynchronous transmission mode cell. a) processing the received subscriber information signal into a variable length packet using a first processor; b) transmitting the variable length packet via a transmission line from the first processor to a first packet converter; c) converting the variable length packet into a cell using the first packet converter; And d) forwarding the cells to a next destination using a system router. The method of claim 14, a) after being routed by the system router, converting the cells back into variable length packets using a second packet converter; b) processing said variable length packet into a next transmission format using a second signal processor; And c) transmitting the result signal to a next destination. The method of claim 15, a) processing the received subscriber information signal into a variable length packet using the second signal processor; b) converting the variable length packet into a cell using the second packet converter; c) forwarding the cells to their intended destination port using the system router; d) converting the cells back into variable length packets using the first packet converter; e) transmitting said variable length packet to a first signal processor across a transmission line; f) processing the variable length packet in a next transmission format; And g) transmitting the result signal to a next destination. 17. The method of claim 16, wherein the variable length packet is a high-level data link control variable length packet. 18. The method of claim 17, wherein the cell is an asynchronous transmission mode cell. 17. The method of claim 16, wherein the cell is an asynchronous transmission mode cell. 17. The method of claim 16, wherein the subscriber information signal received and transmitted by the first signal processor is a code division multiple access spread spectrum signal. 21. The subscriber of claim 20 wherein the subscriber signal received and transmitted by the second signal processor using a selector bank subsystem as the second signal processor to provide a unique transport channel for each individual subscriber information signal. And time-division multiplexing the information signal. 17. The subscriber of claim 16, using a selector bank subsystem as the second signal processor to provide a unique transport channel for each individual subscriber information signal. And time-division multiplexing the information signal. a) routing the received cell to the first packet converter using a system router; b) converting the cell into the variable length packet using the first packet converter; c) transmitting said variable length packet to a first signal processor via a transmission line; d) processing said variable length packet into a next transmission format using said first signal processor; And e) transmitting the result signal to a next destination. The method of claim 23, a) processing the received subscriber information signal into a variable length packet using a second signal processor; b) converting the variable length packet into a cell using a second packet converter; And c) transmitting the cell to the system router.