Wireless packet transfer system using leased channels

Abstract: A packet transfer system for transferring data from or to a plurality of terminals while sectioning the data into given data-length packets, the system having a communication system that has the plurality of terminals, a base station connected through a wireless line with the plurality of terminals and a switching office connected through one or more wired lines with the base station, the wired lines being of shared channels that the plurality of terminals can use commonly and a leased channel that one terminal can use exclusively, When the amount of data transferred from or to one of the plurality of terminals is greater than a predetermined value, one of the shared channels is assigned exclusively to the one of the plurality of terminals or the leased channel is assigned to the one of the plurality of terminals.

Description: Packet transfer systems, where data are transferred within a wired section of communication network while being sectioned into given data-length packets each of which is provided with a destination code, are of a connectionless type in which without establishing a line when calling a packet, packet data are transferred using a shared channel and of a connection-oriented type in which a leased channel is assigned to each user when calling a packet and then packet data are transferred using the leased channel. FIG.1 is an illustration showing a connectionless type packet transfer system. As shown in FIG. 1, a communication system in which the conventional connectionless type packet transfer system is applied is composed of multiple terminals 110a to 110c, a wireless base station 120 that is connected through wireless lines with the terminals 110a to 110c, and a packet switching office 130 that is connected through wired packet lines with the wireless base station 120. The packet switching office 130 is connected with a network 140. such as a packet network as a public network and PSTN as a circuit switched network. Also, in the packet switching office 130, packet terminal equipment 135 to perform a Layer 2 protocol terminal function is provided, where the other Layer 2 protocol terminal function is performed by the terminals 110a to 110c. In the communication system using the connectionless type packet transfer system, all the lines between the wireless base station 120 and the packet switching office 130 are used as shared channels that the multiple terminals 110a to 110c can use commonly. So, through one channel, the transferring of packet data by the terminals 110a to 110c may be performed. FIG.2 is an illustration showing a connection-oriented type packet transfer system. As shown in FIG.2, a communication system in which the conventional connection-oriented type packet transfer system is applied is similar to that in FIG.1. In the communication system using the conventional connection-oriented type packet transfer system, when calling a packet, multiple channels between the wireless base station 120 and the packet switching office 130 are used as leased channels each of which can be used by only one of the terminals 110a to 110c, where the transferring of packet data by the terminals 110a to 110C can be performed using the leased channels assigned to the respective terminals 110a to 110c. However, in the conventional packet transfer systems, the following problems may occur. (1) in the connectionless type packet transfer system, since one channel is used commonly by multiple users, the utilization efficiency per one channel is enhanced. However, the retransmission throughput for guaranteeing the packet data of multiple users at that channel must be reduced. (2) In the connection-oriented type packet transfer system, since One channel is assigned to one user, the retransmission throughput at that channel is enhanced. However, since the leased channel is used exclusively by one user from calling to releasing of packet, the hard physical quantity must increase. Also, when packet data are transferred intermittently, the leased channel will be established even when there is no data transferred. Therefore, the ineffective reserved hard resource must increase. Here, for the packet communications, the per-unit charging system (charging based on the amount of information transferred) is employed in place of the time charging system (charging based on the time during the line is used) for line switching. Therefore, in the above case, a wasteful cost will occur. The document "Dimensioning of Communication Links for Base-station and MSC Interconnection in CDMA Mobile Communication Systems" of Khaled M. F. Elsayed, relates to CDMA mobile communication systems, wherein voice is encoded and packaged in variable length packets that are transported between the mobile station and the switching center. It discusses the link dimensioning for a typical CDMA system and considers a communication link connecting a CDMA base station and Mobile Switching Center. Accordingly, it is an object of the invention to provide a packet transfer system by which packet data can be transferred efficiently without reducing the retransmission throughput of a line and without increasing the hard physical quantity. The object of the invention is achieved with the features of the claims. In this invention, when the amount of data transferred from or to a terminal is greater than a predetermined value, one of shared channels is assigned exclusively to the terminals and data is transferred from or to the terminal using only the assigned channel. Thus, in normal packet transferring, the communications are performed using the shared channel in the leased mode, and when specific-calling traffic increases, one of shared channels is switched into a leased mode so that only the specific calling uses the channel. Since only the specific calling is transferred using the channel, packet data can be transferred efficiently without reducing the retransmission throughput of the line and without increasing the hard physical quantity. Alternatively, when the amount of data transferred from or to a terminal is greater than a predetermined value, a leased channel that one terminals can use exclusively is assigned to the terminal and data is transferred from or to the terminal using only the leased channel. Thus, in normal packet transferring, the communications are performed using the shared channel in the leased mode, and when specific-calling traffic increases, the leased channel is newly assigned to the specific calling. Since only the specific calling. is transferred using the leased channel, packet data can be transferred efficiently without reducing the retransmission throughput of the line and without increasing the hard physical quantity. The invention will be explained in more detail in conjunction with the appended drawings, wherein: FIG.1 is an illustration showing a conventional connectionless type of packet transfer system, FIG.2 is an illustration showing a conventional connection-oriented type of packet transfer system, FIG.3 is an illustration showing a packet transfer system. FIG.4 is a block diagram showing the composition of a wireless base station in FIG.3, FIG. 5 is a flow chart showing an operation of the packet transfer system in FIG.3, FIG.6 is an illustration showing a packet transfer system. FIG. 7 is a block diagram showing the composition of a wireless base station in FIG.6, and FIG.8 is a flow chart showing an operation of the packet transfer system in FIG.6. The preferred embodiments of the invention will be explained below, referring to the drawings <First example> FIG.3 is an illustration showing a packet transfer system in the first preferred embodiment. The system in the first example is, as shown in FIG.3, composed of multiple terminals 10a to 10c, a wireless base station 20 that is connected through wireless lines with the terminals 10a to 10c, and a packet switching office 30 that is connected through wired lines with the wireless base station 20. The packet switching office 30 is connected with a network 40, such as a packet network, e.g. a public network and PSTN as a circuit switched network. Also, in the packet switching office 30, packet terminal equipment 35 to perform a Layer 2 protocol terminal function is provided, where the other Layer 2 protocol terminal function is performed by the terminals 10a to 10c. Although in FIG. 3 only the three terminals 10a to 10c are shown other terminals may also exist. In this example, the wired lines connecting the wireless base station 20 with the packet switching office 30 are of a shared channel type that multiple terminals can use commonly. Meanwhile, in the shared channels, channels equal to the sum of the number of users who use currently the packet transfer and the number of a predetermined percentage of users (non-packet-transfer users) who have the packet transfer contract and do not use currently the packet transfer are established. They are always ready to transfer packets. The total number is predetermined in reference to the number of peak-hour calls on the previous day. Also, the shared channels in this embodiment can be set to a shared mode so that multiple terminals can use the channel commonly and a leased mode so that one terminal uses the channel exclusively FIG.4 is a block diagram showing a composition of the wireless base station 20 in FIG.3. As shown in FIG.4, the wireless base station 20 is composed of counters 21a to 21c each of which counts packet data transferred from the corresponding one of the terminals 10a to 10c, mode switching sections 23-1 to 23-n that are provided for the respective shared channels and switch the mode of shared channel into the shared mode or leased mode, and a control section 22 that compares the count values of the counters 21a to 21c with a predetermined value and controls the operation of the mode switching sections 23-1 to 23-n based on the comparison result. . The operation of the packet transfer system thus composed is explained below. FIG.5 is a flow chart showing the operation of the packet transfer system in FIG.3. When the packet transfer at the terminals 10a to 10c starts (step S1), the counters 21a to 21c of the wireless base station 20 count packet data transferred from the terminals 10a to 10c. Then, in the control section 22 of the wireless base station 20, the count values at the counters 21a to 21c are compared with a predetermined value, and it is judged whether the amount of packet data transferred from the terminals 10a to 10c is greater than the predetermined value or not (step S2). Meanwhile, to each of packet data transferred from the terminals, a user ID to indicate each user is added. Also, the predetermined value, which is the criteria of judgement, can be changed according to the number of callings. When it is judged that the amount of packet data transferred from one of the terminals 10a to 10c at step S2 is greater than the predetermined value, through the shared channel, the control section 22 requests the packet switching office 30 to set one of the shared channels into the leased mode and to assign it to that terminal (step S3) . For example, in this embodiment, it is assumed that the amount of packet data transferred from the terminal 10c is greater than the predetermined value. In this case, through the shared channel, the control section 22 of the wireless base station 20 requests the packet switching office 30 to set one of the shared channels into the leased mode and to assign it to the terminal 10c. Meanwhile, the channel used for requesting its assignment it to the terminal 10c is different from the channel used in transferring that request from the control section 22 of the wireless base station 20 co the packet switching office 30. Then, in the packet switching office 30, it is judged whether one of the shared channels is allowed to be set to the leased mode and to be assigned to the terminal 10c or not (step S4). when at step S4 it is judged that one of the shared channels is allowed to be set to the leased mode and to be assigned to the terminal 10c, this judgement is sent to the control section 22 of the wireless base station 20. Then, by the control of the control section 22, of the mode switching sections 23-1 to 23-n, a mode switching section provided for the shared channel to be set to the leased mode is controlled to operate. Thereby, the concerned shared channel is set to the leased mode, and then the packet data is transferred from the terminal 10c, using the shared channel set to the leased mode (step S5). On the other hand, when at step S2 it is judged that the amount of packet data transferred from the terminal 10c are fewer than the predetermined value, or when at step S4 it is judged that none of the shared channels is not allowed to be set to the leased mode and to be assigned to the terminal 10c, the packet data is transferred using the shared channel of shared mode (step S6). Meanwhile, in this embodiment, since the amount of packet data transferred from the terminals 10a, 10b are fewer than the predetermined value, for the terminals 10a, 10b, the packet data are transferred using the shared channel of shared mode. Also, in transferring packet data from the packet switching office 30 to the wireless base station 20, similar operations to those described above are conducted. In this case, the Layer 2 protocol termination is conducted between the terminals 10a to 10c and the packet terminal equipment 35. The retransmission control for when retansmission is required including the wireless section is conducted by the Layer 2 protocol, for each user ID. This user ID is administered by an anchor packet switching office (not shown) where ID does not change even when a hand-over etc. occurs. After completing the transferring of packet data, the number of shared channels set to the shared mode is detected, and based on the channel number detected, the shared channel set to the leased mode is returned to the shared mode or released. <Second example> FIG.6 is an illustration showing a packet transfer system in the second preferred embodiment. FIG.7 is a block diagram showing a composition of a wireless base station 50 in FIG.6. As shown in FIGS.6 and 7, this example has a composition similar to that in FIG.3, except for the wireless base station 50. The wired lines to connect the wireless base station 50 and the packet switching office 30 are composed of shared channels that multiple terminals can use commonly and a leased channel that one terminal can use exclusively. Also, the wireless base station 50 in this embodiment is, as shown in FIG.7, composed of counters 51a to 51c each of which counts packet data transferred from the corresponding one of the terminals 10a to 10c, and a control section 52 that compares the count values of the counters 51a to 51c with a predetermined value and controls the setting of the shared channels and leased channel based on the comparison result. The operation of the packet transfer system in this example is explained below. Fig. 8 is a flow chart showing the operation of the packet transfer system in FIG.6. When the packet transfer at the terminals 10a to 10c starts (step S11), the counters 51a to 51c of the wireless base station 50 count packet data transferred from the terminals 10a to 10c. Then, in the control section 52 of the wireless base station 50, the count values at the counters 51a to 51c are compared with a predetermined value, and it is judged whether the amount of packet data transferred from the terminals 10a to 10c is greater than the predetermined value or not (step S12). Meanwhile, to each of packet data transferred from the terminals, a user ID to indicate each property is added. Also, the predetermined value, which is the criteria of judgement, can be changed according to the number of callings. When at step S2 it is judged that the amount of packet data transferred from one of the terminals 10a to 10c is greater than the predetermined value, the control section 52 requests the packet switching office 30 to assign the leased channel to that terminal (step s13). . For example, in this embodiment, it is assumed that the amount of packet data transferred from the terminal 10c is greater than the predetermined value. In this case, through the shared channel, the control section 52 of the wireless base station 50 requests the packet switching office 30 to assign the leased channel to the terminal 10c. Then in the packet switching office 30, it is judged whether the leased channel is allowed to be assigned to the terminal 10c or not (step S14). When at step S14 it is judged that the leased channel is allowed to be assigned to the terminal 10c, this judgement is sent to the control section 52 of the wireless base station 50. Then, by the control of the control section 52, the leased channel is assigned to the terminal 10c, and then the packet data is transferred from the terminal 10c, using the leased channel (step S15). Here, when the packet data is transferred using the leased channel, since the terminal and the leased channel are corresponding to each other in one-to-one relation, no user ID is necessary to add to the packet data. On the other hand, when at step S12 it is judged that the amount of packet data transferred from the terminal 10c is less than the predetermined value, or when at step S14 it is judged that the leased channel is not allowed to be assigned to the terminal 10c, the packet data, is transferred using the shared channel (step S16). Meanwhile, in this embodiment, since the amount of packet data transferred from the terminals 10a, 10b are fewer than the predetermined value, for the terminals 10a, 10b, the packet data are transferred using the shared channel. Also, in transferring packet data from the packet switching office 30 to the wireless base station 50, similar operations to those described above are conducted. In this case, the Layer 2 protocol termination is conducted between the terminals 10a to 10c and the packet terminal equipment 35. In case where the retransmission is required for the sections including the wireless transmission section, the retransmission control is conducted between the Layer 2 protocol terminals for each user ID. This user ID is administered by an anchor packet switching office (not shown) where ID does not change even when a hand-over etc. occurs After completing the transfer of packet data, the leased channel is released. <Third example> In the first and second examples described above, it is judged at the wireless base station whether the packet data transferred from each of the terminals 10a to 10c is greater than the predetermined value. However, when the amount of packet data transferred from each of the terminals 10a to 10c is greater than the predetermined value, such information may be added at the terminals 10a to 10c to the packet data and then transferred to the wireless base station with the packet data. Then, the control section of the wireless base station may detect the information, and based on the information the mode switching for setting the shared channel or the leased channel can be performed. For such a case, the counters 21a to 21c and 51a to 51c are not necessary. The information about whether the amount of packet data transferred from each of the terminals 10a to 10c is greater than the predetermined value is sent directly to the control section 22, 52 from the terminals 10a to 10c. Based on the information, the control section 22, 52 operates. Advantages of the Invention: (1) When the amount of data transferred from or to the terminal is greater than a predetermined value, one of shared channels is assigned exclusively to the terminal and the data transferred from or to the terminal is transferred using only the assigned channel. Therefore, without reducing the retransmission throughtput of the line and without increasing the hard physical quantity, the packet data can be transferred efficiently. (2) When the amount of data transferred from or to the terminal is greater than a predetermined value, a leased channel that only one terminal can use is assigned to the terminal and the data transferred from or to the terminal is transferred using only the leased channel. Therefore, the same effect as described above can be obtained. Also, since no user ID is necessary to add to the packet data, the data transfer in the wired section can be made more efficient.

Claims: A packet transfer system for transferring data from and/or to a plurality of terminals (10a, 10b, 10c) while sectioning said data into given data-length packets, comprising: a communication system that is composed of said plurality of terminals (10a, 10b, 10c), a base station (20; 50) connected through a wireless line with said plurality of terminals (10a, 10b, 10c) and a switching office (30) connected through one or more wired lines with said base station (20; 50), said wired lines being composed of shared channels that said plurality of terminals (10a, 10b, 10c) can use commonly; wherein said base station (20; 50) is composed of means (21a, 21b, 21c; 51a, 51b, 51c) for counting packet data transferred from said plurality of terminals (10a, 10b, 10c), said counting means (21a, 21b, 21c; 51a, 51b, 51c) being provided for each of said plurality of terminals, a mode switching means (23-x) for switching said shared channels into a shared mode that said plurality of terminals (10a, 10b, 10c) can use commonly or a leased mode that one of said plurality of terminals can use exclusively, said mode switching means (23-x) being provided for each of said shared channels, and a control means (22; 52) for comparing a count value of said counting means (21a, 21b, 21c; 51a, 51b, 51c) with a predetermined value and controlling the operation of said mode switching means (23-x) based on the comparison result, wherein said control means (22; 52)when the count value of said counting means (21a, 21b, 21c; 51a, 51b, 51c) is greater than said predetermined value, controls said mode switching means (23-x) to switch one of said shared channels into the leased mode that the concerned one of said plurality of terminals (10a, 10b, 10c) can use exclusively. A system according to claim 1, comprising additionally a leased channel that only one of said plurality of terminals (10a, 10b, 10c) can use; wherein said control means (22; 52) when the count value of said counting means (21a, 21b, 21c; 51a, 51b, 51c) is greater than said predetermined value, controls said additional leased channel to be assigned to the concerned one of said plurality of terminals (10a, 10b, 10c). A system according to claim 1 or 2, wherein: said predetermined value is alterable according to the number of callings.

Inventors: UEDA HITOSHI, UEDA, HITOSHI
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1999
Main classification: H04L12
IPC codes: H04L12, H04W92