Packet transmission method and system, base station, wireless LAN terminal, and wireless LAN system using the same

Disclosed herein is a packet transmission method wherein received packets are sorted into prioritized QoS packets and general packets other than the prioritized QoS packets, the sorted prioritized QoS packets are accumulated, the accumulated QoS packets are capsulated and then transmitted as a capsulated packet, and the capsulated packet is transmitted in matching with the period of a CODEC. In the preferred embodiment, there is provided a wireless LAN system comprising a base station and at least one wireless LAN terminal connected to said base station via a wireless LAN; and a packet transmission system for transmitting a packet between said base station and said at least one wireless LAN terminal via the wireless LAN, the packet transmission system. In the packet transmission system, a packet sorter sorts received packet into prioritized packets and packets other than the prioritized packets. A FIFO queue buffer (QoS queue) accumulates the sorted prioritized packets. A packet combiner capsulates the accumulated packets in the QoS queue. A wireless packet transmitter transmits the capsulated packet between the base station and the at least one wireless LAN.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a packet transmission method and system for transmitting received packets, and a base station, a wireless LAN (Local Area Network) terminal, and a wireless LAN system using the same.

2. Description of the Related Art

FIG. 14is a block diagram showing a configuration of a wireless LAN system according to a prior art example. Real time communication such as VoIP (Voice on Internet Protocol) via a conventional wireless LAN will be explained with reference toFIG. 14. InFIG. 14, terminals1301,1302, . . . ,130N respectively have a CODEC (COder-DECoder) and a network interface for transmitting and receiving packets1,2, . . . , N for data communication and real time communication. A network1310consists of Internet or a LAN or the like capable of IP (Internet Protocol) communication and transmits data packets and RTP (Real Time Protocol) packets.

Packets1311(packets1,2, . . . , N) correspond to RTP packets transmitted from the terminals1301,1302, . . . ,130N and transfer media data such as voice, moving pictures to individual destinations. A base station1320bridges the packets1311(RTP packets) transmitted through the network1310to a wireless LAN. Wireless LAN packets1321,1322, . . . ,132N comprise wireless LAN headers and payloads1,2, . . . , N respectively, and correspond to RTP packets bridged to the wireless LAN and transfer real-time communication data such as voice, moving pictures to wireless LAN terminals1331,1332, . . . ,133N. The wireless LAN terminals1331,1332, . . . ,133N decode the received wireless LAN packets1321,1322, . . . ,132N (RTP packets) to reproduce the media data such as voice, moving pictures respectively.

SUMMARY OF THE INVENTION

However, the real time communication such as the VoIP via the conventional wireless LAN had the following problems. That is, since the wireless LAN headers were large and the RTP packets were of short packets, the original transmission rate could not be utilized. Since there was no matching between communication timing of the wireless LAN and the period of a CODEC, the efficient transmission of packets could not be carried out.

The present invention has been made in view of the conventional problems, and an object of the present invention is therefore to provide a packet transmission method and system capable of taking advantage of the original transmission rate and transmitting packets with efficiency, a base station equipment, a wireless LAN terminal equipment and a wireless LAN system each of which makes use of the packet transmission method and system.

In order to attain the above object, according to one aspect of the present invention, there is provided a packet transmission method comprising the steps of sorting received packets into prioritized packets and packets other than the prioritized packets, and transmitting the sorted prioritized packets.

According to another aspect of the present invention, there is provided a packet transmission method comprising the steps of sorting received packets into prioritized packets and packets other than the prioritized packets, accumulating the sorted prioritized packets, capsulating the accumulated packets, and transmitting the so-capsulated packet.

According to a further aspect of the present invention, there is provided a packet transmission system comprising sorting means for sorting received packets into prioritized packets and packets other than the prioritized packets, and transmitting means for transmitting the prioritized packets sorted by the sorting means.

According to a yet another aspect of the present invention, there is provided a packet transmission system comprising sorting means for sorting received packets into prioritized packets and packets other than the prioritized packets, accumulating means for accumulating the prioritized packets sorted by the sorting means, capsulating means for capsulating the packets accumulated in the accumulating means, and transmitting means for transmitting the packet capsulated by the capsulating means.

According to a still further aspect of the present invention, there is provided a base station equipment including the above packet transmission system.

According to a still further aspect of the present invention, there is provided a wireless LAN terminal equipment including the above packet transmission system.

According to a still further aspect of the present invention, there is provided a wireless LAN system comprising the above base station equipment, and the above wireless LAN terminal equipment.

According to a still further aspect of the present invention, there is provided a wireless LAN system comprising the above base station equipment, the above wireless LAN terminal equipment connected to the base station equipment via a wireless LAN, and arbitrating means for transmitting delay request information for delaying transmission of packets from the base station equipment to the wireless LAN terminal equipment such that the packet transmission does not overlap with other terminals thereby to arbitrate transmission of packets from the wireless LAN terminal equipment to the base station equipment so as not to cause a collision thereof.

According to a still further aspect of the present invention, there is provided a wireless LAN system comprising the above base station equipment, and the above wireless LAN terminal equipment connected to the base station equipment via a wireless LAN, wherein the wireless LAN terminal equipment is associated with a PCF mode, and the base station equipment sets a NAV time and gives timing provided to transmit a capsulated packet, to the wireless LAN terminal equipment.

According to a still further aspect of the present invention, there is provided a wireless LAN system comprising the above base station equipment, and the above wireless LAN terminal equipment connected to the base station equipment via a wireless LAN, and means for adjusting a period for transmitting a capsulated packet according to the number of real time sessions active via the base station equipment.

According to a still further aspect of the present invention, there is provided a wireless LAN system comprising the above base station equipments, the above wireless LAN terminal equipments respectively connected to the base station equipments via a wireless LAN, and means for collecting CODEC minimal periods corresponding to the number of the wireless LAN terminal equipments set every above base station equipments and adjusting the longest CODEC period of the resultant minimal periods as a transmission period of each capsulated packet.

According to a still further aspect of the present invention, there is provided a wireless LAN system comprising an IP exchanger having the above packet transmission system, the above base station equipments connected to the IP exchanger, the above wireless LAN terminal equipments respectively connected to the base station equipments via a wireless LAN, a table in which IP addresses of the wireless LAN terminal equipments connected every above base station equipments and information indicative of whether the wireless LAN terminal equipments are able to receive capsulated packets are registered, and means for performing control for, when transmit destination IP addresses of received packets respectively correspond to IP addresses of the wireless LAN terminal equipments and the wireless LAN terminal equipment are respectively able to receive the capsulated packets, allowing the IP exchanger to capsulate prioritized packets, based on the information registered in the table and causing the IP exchanger to transmit the so-capsulated packet, and allowing the IP exchanger to transmit the received packets to the base station equipments as they are if not so.

According to a still further aspect of the present invention, there is provided a wireless LAN system comprising the above base station equipment, the above wireless LAN terminal equipment connected to the base station equipment via a wireless LAN, arithmetic means for computing use efficiency of a general queue for accumulating general packets other than prioritized capsules, using a predetermined arithmetic expression, and control means for changing coefficients of the arithmetic expression according to the state of accumulation of the general queue to thereby control the value of the use efficiency computed by the arithmetic means.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will next be described in detail with reference to the accompanying drawings. In the following embodiments, there is provided a packet transmission system having a wireless LAN base station and wireless LAN terminals connected to the station via a wireless LAN. Each of the terminals has CODEC (COder-DECoder) module (hereinafter called “CODEC”) composed of software or hardware for converting analogy signals such as voice, moving pictures into digital form, compressing and expanding or decompressing the same in order to perform real time communication. The system is intended to improve the efficiency of transmission of a RTP (Real Time Protocol) packet and ensure QoS (Quality of Service) of the real time communication, and increase an allowable number of communications while compressing the number of packets on the wireless LAN, matching between the transmission period of each packet and the period time of the CODEC, and holding communications of each normal LAN packet (hereinafter called a “general packet”).

First Embodiment

FIG. 1is a block diagram showing a first embodiment of the present invention. InFIG. 1, terminals101,102, . . . ,10N respectively have CODECs and network interfaces and transmit and receive packets1,2, . . . , N for data communication and real time communication. A network110comprises Internet or a LAN or the like, which is capable of IP communication and transmits RTP packets and general packets.

Packets111(packets1,2, . . . , N) are RTP packets transmitted from the terminals101,102, . . . ,10N and transfer media data such as voice, moving pictures to individual destinations. A base station120includes QoS queues (refer to a subsequent description) that accumulate the packets111(RTP packets) transmitted from the network110and process the same on a priority basis, and an interval timer (refer to a subsequent description) that counts a period T obtained in the following expression (1) with respect to the period C of the CODEC used for generation of RTP packets. A period d in the following expression (1) indicates the minimum interval for avoiding interference with the reception of each terminal.
d≦T≦C  (1)

The base station120capsulates the received packets111(RTP packets) accumulated at intervals of the period T as denoted by a packet121and sends out the packet (hereinafter called a capsulated packet”)121to a communication channel on the wireless LAN with the timing of the period T. Particularly when small packets like voice RTP packets are periodically sent one by one, the RTP packets of each session are combined into one, which in turn is transmitted as a broadcast or multicast capsulated packet121(hereinafter called “broadcast capsulated packet”) in a mode requiring no ACK reply.

Each of wireless LAN terminals131,132, . . . ,13N has the mechanism of extracting a LAN packet addressed thereto from the broadcast capsulated packet121sent from the base station120, and decodes the extracted RTP packet to reproduce or play back media data such as voice, moving pictures. In the present embodiment as described above, the RTP packets are transmitted with timing matched with the period of the CODEC while compressing the number of the packets transmitted over the wireless LAN.

In general, a header section in the wireless LAN packet is large in band consumption. In IEEE802.11b, for example, the header section is modulated with 1 Mbps. Converting to 11 Mbs results in one equivalent to more than or equal to 256 bytes. In contrast, the RTP packet results in a relatively small packet. When a voice of 10 ms is coded on the basis of G. 729, for example, a payload is no more than 10 bytes, thus resulting in one-twentieth of the wireless LAN packet.

Further, a UDP (User Datagram Protocol) is applied to each RTP session using the RTP packet. Since the ACK reply occurs in a unicast on the wireless LAN, its header also presses the band. Thus when a large number of RTP sessions are developed or broadcasted through the wireless LAN, the transmission and reception of a short packet frequently occur and hence its header increases markedly in band consumption, so that the quality of voice and moving pictures is degraded.

The present embodiment improves such a point, compresses the number of packets on the wireless LAN and matches between the packet transmission period and the period of CODEC to enhance the efficiency of transmission, thereby making it possible to improve the communication quality of voice and moving pictures or the like and the number of simultaneous communications in real time communication even under wireless LAN environments utilized by a large number of terminals such as offices, hot spots.

FIG. 2is a block diagram showing the base station120and wireless LAN terminals131through13N ofFIG. 1in detail. InFIG. 2, a packet receiver201in the base station120receives packets from the network110. A packet sorter202refers to headers of the received packets and sort them into prioritized packets (hereinafter called “QoS packets”) and general packets other than those.

A method of sorting the packets by the packet sorter202will be described later in detail. A FIFO (First-In First-Out) queue buffer (hereinafter called general queue)204for the general packets temporarily accumulates the unprioritized packets therein. FIFO queue buffers (hereinafter called “QoS queues”)205for the QoS packets temporarily accumulate the prioritized packets therein.

A packet combiner206capsulates the packets accumulated in the QoS queues205in preference to the packets accumulated in the general queue204. An interval timer207measures time of the period T (refer to the expression (1)) for providing timing to generate the capsulated packet. A wireless packet transmitter208transmits the general packets and capsulated packet to a wireless section.

A wireless packet receiver211in each of the wireless LAN terminals131through13N receives wireless packets from the base station120. When a packet reconstructor212receives the capsulated packet therein, it extracts and reconstructs the corresponding packet addressed thereto from within the capsulated packet. An application220performs real time communication through the use of the CODEC in addition to the normal transmission of data.

A packet sorter222refers to the packets required to be transmitted from the application220and sorts them into the QoS packets and general packets. The packet sorter222performs sorting of the QoS packets and general packets in a manner similar to the packet sorter202.

A QoS queue223temporarily accumulates the QoS packets therein. A general queue224temporarily accumulates the general packets therein. An interval timer225ticks the period T (see the expression (1) referred to above). A packet combiner226is capable of capsulating the packets accumulated in the QoS queue223in preference to the packets accumulated in the general queue224. A wireless packet transmitter227transmits the normal packets and capsulated packet to the wiring section.

A wireless packet receiver230in the base station120receives a wireless LAN packet therein. When a packet reconstructor231receives the capsulated packet, it extracts and reconstructs all of the packets contained therein. A packet transmitter232transmits the packets to the network110.

Here, the QoS queues205in the base station120are divided every MAC (Media Access Control) addresses, IP addresses or IP ports. In case of need, the QoS queues205are further divided every types of RTP packets, and the packets are read in preference to the general queue204in principle. When the packet combiner206processes short packets that periodically arrive one by one as in the case of the voice RTP packets, it may capsulate the RTP packets for respective destinations, combine the broadcast or multicast capsulated packets and control the wireless packet transmitter208to synchronize the interval between radio beacons with the period T.

Alternatively when it is desired to process short packets that arrive in large numbers periodically with respect to one destination as in the case of RTP packets of moving pictures, the packet combiner206may capsulate only the RTP packets for the destination and combine unicast capsulated packets. Also the packet combiner206may pass long packets ineffective for capsulation, as they are without capsulating them. This is similar even to the general queues. The packet combiner206delivers both capsulated packets and normal packets to the packet transmitter208according to cases. On the other hand, since the destination for each wireless packet is directed only to the base station120, the packet combiners226in the wireless LAN terminals131through13N always handle the capsulated packets as unicasts.

Incidentally, while the general queue204in the base station120is provided collectively as one in the present embodiment, the general queue204may be divided every destination MAC addresses. Timings provided for the radio beacons may be used as the timings provided to generate the capsulated packets by the respective interval timers207and225of the base station120and the wireless LAN terminals131through13N.

A description will next be made of the operation of transmitting packets between the base station120and each of the wireless LAN terminals131through13N inFIG. 2. When the packets are first supplied from the packet receiver201to the packet sorter202in the base station120, the packet sorter202sorts the packets according to a method to be described later. If they are found to be general packets, then the packet sorter202supplies the packets to the general queue204. If they are found to be QoS packets at the existing QoS session, then the packet sorter202supplies the packets to the QoS queues205. If they are judged to be QoS packets at a new QoS session, then the packet sorter202creates a new queue buffer within the QoS queues205and supplies the packets thereto.

The interval timer207has already counted the period T. When timing is supplied from the interval timer207to the packet combiner206, the packet combiner206takes out the packets from the general queue204and the QoS queues205on a QoS packet priority basis and capsulates them, followed by supply to the wireless packet transmitter208. Incidentally, since their capsulation is ineffective where they are long packets even in the case of the QoS packets, the packet combiner206may not capsulate them.

On the other hand, when each packet sent from the wireless packet transmitter208is received by each of the wireless LAN receivers211in the wireless LAN terminals131through13N, and the received packet is supplied from the wireless packet receiver211to the packet reconstructor212, the packet reconstructor212makes a decision as to whether the packet is a capsulated packet. If the packet is found to be a general packet at this time, then the packet reconstructor212supplies the packet to the application220. If the packet is found to be the capsulated packet, then the packet reconstructor212determines whether it is a broadcast packet. If it is found to be a unicast packet, then the packet reconstructor212reconstructs all the packets with which the unicast packet is packaged, and supplies them to the application220. If it is found to be a broadcast packet, then the packet reconstructor212determines destinations for packets with which the broadcast packet is packaged. If the packet addressed to the packet reconstructor212exists therein, then the packet reconstructor212reconstructs the packet and supplies it to the application220.

Next, when the packet is supplied from the application220to the packet sorter222, the packet sorter222similarly performs a decision as to the packet. If the packet is found to be a general packet, then the packet sorter222supplies it to the general queue224. If the packet is found to be a QoS packet, then the packet sorter222supplies it to the QoS queue223.

The interval timer225has already counted the period T. When timing is supplied from the interval timer225to the packet combiner226, the packet combiner226takes out the packets from the general queue224and the QoS queue223on a QoS packet priority basis and capsulates them, followed by supply to the wireless packet transmitter227. Since, even at this time, there is no effect on their capsulation where they are long packets, the packet combiner226may not capsulate them.

When the corresponding packet received from the wireless packet transmitter227is supplied from the wireless packet receiver230to the packet reconstructor231in the base station120, the packet reconstructor231determines whether it is of a capsulated packet. If the packet is found to be a general packet, then the packet reconstructor231supplies the packet to the packet transmitter232. If the packet is found to be of the capsulated packet, then the packet reconstructor231reconstructs all the packets with which the capsulated packet is packaged, and supplies them to the packet transmitter232.

A method of sorting packets by the packet sorters202and222in the base station120and the wireless LAN terminals131through13N will next be explained.FIG. 3is a flowchart showing one example of a packet sorting process to be executed by each of the packet sorters202and222. Incidentally, as will be descried later, the packet sorters202and222have a QoS cache table301and a QoS setting table302therein respectively in the present embodiment. Each of the packet sorters202and222performs a process for sorting received packets into QoS packets and general packets by using the two tables301and302.

InFIG. 3, when the packet sorters202and222first receive packets, they refer to the QoS table301and determine whether the received packets have been registered therein (Step S301). That is, IP addresses and IP ports for packets have been registered in the QoS cache table301. When the IP addresses and IP ports of headers for the received packets have been registered therein, the packet sorters202and222determine that the received packets have been registered in the QoS cache table301. Incidentally, the QoS cache table301is empty in its initial state. In this case, the packet sorters202and222judge that the packets have not been registered.

Next, the packet sorters202and222respectively perform a setting process using the QoS setting table302(Step S302).FIG. 4is a flowchart showing the process of Step S302in detail. Incidentally, TCP(Transmission Control Protocol)/UDP(User Datagram Protocol) patterns of packets, IP ports thereof, MAC addresses thereof, voice, moving picture patterns, etc. have been registered in the QoS setting table302. First, the packet sorters202and222refer to headers (headers for layer4) of received packets and check the same against the TCP/UDP patterns registered in the QoS setting table302to thereby determine whether the received packets are TCP or UDP (Step S401).

When the received packets are found to be TCP at Step S401, the packet sorters202and222proceed to Step S306inFIG. 3, where they determine that the received packets are of general packets. Then the packet sorters202and222respectively sort them into the general queues204and224and terminate the packet sorting process. On the other hand, when the received packets are found to be UDP at Step S401, the packet sorters202and222refer to UDP headers of the received packets and determine whether IP ports at the headers respectively coincide with the IP ports registered in the QoS setting table302(Step S402).

When they are found not to coincide with the IP ports at this time, the packet sorters202and222refer to headers (headers for layer2) of received packets and thereby determine whether MAC addresses thereof have been registered in the QoS setting table302(Step S403). When the MAC addresses are found not to have been registered therein, the packet sorters202and222determine at Step S306inFIG. 3that the received packets are general packets. Then the packet sorters202and222respectively sort the general packets into the general queues204and224and terminate the packet sorting process. When the MAC addresses are found to have been registered therein, the packet sorters202and222proceed to Step S404where they perform a pattern matching process. The present Step S404is however a process executed in embodiments to be described later, where prioritized packets are further sorted into moving pictures and voice packets (Step S404inFIG. 4corresponds to Step S303inFIG. 3).

Thus, in the present embodiment, when the answer is YES at Step S402and the answer is YES at Step S403, the packet sorters202and222perform the pattern matching process (Step S404ofFIG. 4and Step. S303ofFIG. 3) and further sort the prioritized packets into moving picture packets and voice packets. Thereafter, the packet sorters202and222proceed to Step S304, where the IP addresses and IP ports of the received packets are registered in the QoS cache table301. Afterwards, the packet sorters202and222sort the received packets into the priority queues205and223as the prioritized packets (Step S305). Each time the packet sorters202and222receive packets, they respectively perform the processes shown inFIGS. 3 and 4and sort the received packets into the prioritized packets and general packets.

Second Embodiment

A second embodiment of the present invention will next be explained. The present embodiment is designed so as not to cause trouble in real time communication even when overload is imposed on packet transmission. Incidentally, the present embodiment is similar toFIGS. 1 and 2illustrative of the first embodiment in respect to a system configuration and configurations of a base station and wireless LAN terminals.

In the present embodiment, packet sorters202and222respectively set queues every MAC addresses as to general queues204and224as shown inFIG. 5. Thus, since the general queues204and224are queued every MAC addresses, there is no harm in transmitting packets even if the packet transmission to other terminals is congested.

Third Embodiment

A third embodiment of the present invention will next be explained. Although a system configuration and basic configurations of a base station and wireless LAN terminals in the third embodiment are similar toFIGS. 1 and 2illustrative of the first embodiment, the third embodiment is further contriving the transmission of packets from the wireless LAN terminals to the base station.FIG. 6shows a timing chart thereof.

InFIG. 6, an interval timer300of a base station120counts the period T taken to transmit a capsulated packet from the base station120to wireless LAN terminals131,132, . . . ,13N. Interval timers301,302, . . . ,30N of the wireless LAN terminals131,132, . . . ,13N respectively counts timings provided to transmit capsulated packets from the wireless LAN terminals131,132, . . . ,13N to the base station120.

A broadcast capsulated packet310from the base station120to the wireless LAN terminals131,132, . . . ,13N is packaged with packets to be transmitted to the terminals131,132, . . . ,13N and delay request information to the terminals131,132, . . . ,13N. Designated at numerals311,312, . . . ,31N are transmission delay times after the terminals respectively have received the delay request information. Designated at numerals321,322, . . . ,32N are packets transmitted from the terminals131,132, . . . ,13N to the base station120after the terminals respectively have received the broadcast capsulated packet310.

Although a broadcast capsulated packet330transmitted from the base station120to the wireless LAN terminals131,132, . . . ,13N is packaged with packets transmitted to the terminals131,132, . . . ,13N, it does not contain delay request information. Designated at numerals331,332, . . . ,33N are packets transmitted from the wireless LAN terminals131,132, . . . ,13N to the base station120after the terminals respectively have received the broadcast capsulated packet330. When a large number of the terminals131,132, . . . ,13N are performing real time communication under one base station120, the efficiency of transmission of the packets from the base station120to the terminals131,132, . . . ,13N can be enhanced by compressing the number of packets through the use of the broadcast capsulated packets.

However, in the case of a distributed coordination type DCF (Distributed Coordination Function) that has been widely used, the transmission of the packets from the wireless LAN terminals131,132, . . . ,13N to the base station120is apt to frequently produce a packet collision and cause the loss of transmission.

In the present embodiment, when the base station120has recognized the beginning of a session with the wireless LAN terminals131,132, . . . ,13N, the base station120allocates such delay times as not to overlap with those for other terminals131,132, . . . ,13N to the wireless LAN terminals131,132, . . . ,13N in the form of an integral multiple of the time required to receive one packet from each of the terminals131,132, . . . ,13N and notifies the same to the wireless LAN terminals131,132, . . . ,13N as delay request information with being superimposed on the broadcast capsulated packets.

The terminals131,132, . . . ,13N having received the information set their own interval timers301,302, . . . ,30N to the times designated by the delay request information once at the time of their reception and return the interval timers301,302, . . . ,30N to the original period T after timeout. InFIG. 6, the interval timers301,302, . . . ,30N count their delay times311,312, . . . ,31N in response to delay requests and are restored to the period T after the transmission of the packets321,322, . . . ,32N by the terminals131,132, . . . ,13N has been performed in accordance with the timeout. At the next timeout, the terminals131,132, . . . ,13N transmit the packets331,332, . . . ,33N respectively. Since no delay request information is contained in the broadcast capsulated packet330sent from the base station120to the terminals131,132, . . . ,13N, the interval timers301,302, . . . ,30N of the terminals131,132, . . . ,13N respectively continue to tick the period T.

Thus, in the present embodiment, an effect can be obtained that since packet transmissions of the wireless LAN terminals131,132, . . . ,13N are arbitrated so as not to collide, it is possible to suppress the collision of the packets and improve the efficiency of transmission of the wireless LAN.

Fourth Embodiment

A fourth embodiment of the present invention will next be explained. The fourth embodiment is contriving a PCF (Point Coordination Function) mode.FIG. 7is a typical diagram thereof. Incidentally, a system configuration and configurations of a base station and wireless LAN terminals are basically similar toFIGS. 1 and 2.

InFIG. 7, a base station400performs channel control of a wireless LAN. In a manner similar to the base station120according to the first embodiment, the base station400has the function of sorting received packets into QoS packets and general packets, capsulating the QoS packets, and transmitting the so-capsulated packet in matching with the CODEC period. Each of radio beacons401periodically divides a radio channel. A periodic interval402is a periodic interval of the radio beacon401. A NAV (Network location Vector)403notified to wireless LAN terminal groups411and412by the radio beacon401is equivalent to a reserved time from the radio beacon401, which is taken to inhibit packet transmission of the terminal groups411(terminals1,2, . . . , N) and412(terminals (N+1) through M). Also a time404is equivalent to the time required to perform packet transmission under the PCF mode.

A CF_END signal405is a signal for notifying the completion of a PCF period to each terminal. A time406is equivalent to the time taken to perform packet transmission under the PCF mode. A cell410of the wireless LAN is an area where communications with the base station400are enabled. The wireless LAN terminal group411(terminals1,2, . . . , N) based on the PCF mode performs real time communication via the base station400.

Further, the wireless LAN terminal group412(terminals (N+1) through M) is a wireless LAN terminal group based on a DCF (Distributed Coordination Function) mode. The base station400adjusts the beacon interval402to the period T, and sends out a broadcast capsulated packet in synchronism with it when the broadcast capsulated packet exists. Subsequently, the base station400sequentially transmits capsulated packets, general packets or unicast packets each indicative of an ACK request to the terminal group411based on the PCF mode every terminals.

The wireless LAN terminal group411based on the PCF mode and the wireless LAN terminal group412based on the DCF mode respectively have the function of sorting received packets into QoS packets and general packets in a manner similar to the wireless LAN terminals131,132, . . . ,13N employed in the first embodiment, capsulating the QoS packets, and transmitting the so-capsulated packet in matching with the CODEC period.

When one terminal of the terminal group411based on the PCF mode receives a unicast packet from the base station400, it sends back an ACK packet. When a capsulated or general packet to be transmitted exists, the packet is transmitted in accordance with the corresponding ACK.

Thus, since the base station400sets the NAV time and allocates the transmission timings to the terminals based on the PCF mode in the present embodiment, there is no need to allow the terminals to have the interval timers for providing the timings taken to capsulate the packets, and the processing on the terminal side can be reduced. Further, since the transmission of the broadcast capsulated packet to the terminals can be performed in advance, it is possible to lighten a load from the reception of the packet from the base station to the sending back of ACK thereto. Incidentally, the PCF period may be constituted of an HCF period in the present configuration.

Fifth Embodiment

A fifth embodiment of the present invention will next be described. The fifth embodiment is designed so as to be able to ensure the transmission of general packets even when the number of QoS packets increases.FIG. 8shows a typical diagram of a packet transmission sequence employed in the present embodiment. Incidentally, a system configuration and configurations of a base station and wireless LAN terminals both according to the fifth embodiment are similar toFIGS. 1 and 2showing the first embodiment.

InFIG. 8, a broadcast capsulated packet500is such a broadcast capsulated packet sent from a base station120to wireless LAN terminals131through13N that priorities are assigned to QoS packets. A payload of the broadcast capsulated packet500includes a section501consisting of QoS packets, and a section502consisting of a general packet.

A capsulated packet510is a QoS packet-prioritized capsulated packet sent from the wireless LAN terminals131through13N to the base station120. A payload of the capsulated packet510includes a section511consisting of a QoS packet, and a section512consisting of general packets. A capsulated packet520is a broadcast capsulated packet dedicated to general packets, which is sent from the base station120to the terminals131through13N. A payload of the capsulated packet520is made up of a section521consisting of only general packets such as DATA packets.

A capsulated packet530is a capsulated packet dedicated to general packets, which is sent from the wireless LAN terminals131through13N to the base station120. A payload of the capsulated packet530is made up of a section531consisting of only general packets such as DATA packets.

Here, the base station120generates a capsulated packet with priority being assigned to QoS queues. Therefore, if the number of RTP sessions to which QoS is applied increases, then the QoS packet section501increases in the broadcast capsulated packet500and eventually the base station120is not able to create the general packet section502. When the broadcast capsulated packet500is continuously transmitted, the RTP sessions are maintained but the transmission of general data is stopped. The capsulated packet510combined by the terminal side is also similar to the above.

In the present embodiment, as shown inFIG. 8, the capsulated packets dedicated to the general packets are respectively transmitted between the base station120and the wireless LAN terminals131through13N while being interrupted between the QoS packet-prioritized capsulated packets. Incidentally, such packet transmission is performed by the wireless packet transmitters208and227in the base station and wireless LAN terminals ofFIG. 2, for example. In the present embodiment as described above, real time communication can be optimized without impairing the normal use of the wireless LAN because the minimum transmission of the general packets can be ensured.

Sixth Embodiment

A sixth embodiment of the present invention will next be explained. The sixth embodiment is designed so as to be able to adapt to the type of RTP packet to which QoS is applied. Its configuration diagram is shown inFIG. 9. Incidentally, although a system configuration and configurations of a base station and wireless LAN terminals both according to the sixth embodiment are similar to the first embodiment, the present embodiment is different from the first embodiment in that QoS packets are further identified to be RTP packets of moving pictures and voice and then processed according to their identification.

InFIG. 9, a dotted-line section600is used to describe a period taken to generate each voice packet. As shown by the dotted-line section600, a voice CODEC generally generates RTP packets one by one every predetermined periods U. A dotted-line section601is used to explain a period taken to generate each moving picture packet. As shown by the dotted-line section601, a moving picture CODEC generally generates a plurality of RTP packets every predetermined periods U′.

A wireless LAN base station610makes a contrivance for voice/moving picture communications. A packet receiver611is a section for receiving packets from a network. A packet sorter612identifies general packets and QoS packets and further identifies the QoS packets to be RTP packets of moving pictures and voice. A method for sorting the packets by the packet sorter612will be described later.

A general queue614temporarily accumulates therein unprioritized general packets every destination MAC addresses or IP address ports. A moving picture queue615temporarily accumulates therein moving picture packets to which QoS is applied, every destination MAC addresses or IP address ports. A voice queue616temporarily accumulates therein voice packets to which QoS is applied, every destination MAC addresses or IP address ports.

A packet combiner617passes or combines the temporarily-accumulated packets according to a method to be described later. An interval timer618divides the period T equivalent to the greatest common factor of the voice packet periods U and moving picture packet periods U′ and supplies timing provided for packet combination to the packet combiner617. A wireless packet transmitter619sends out the packets passed or transmitted through the packet combiner617or the packet combined by the packet combiner617to a wireless LAN along a period T.

A wireless LAN terminal620makes a contrivance for voice/moving picture communications. An application unit621includes voice and moving picture CODECs and performs real time communication such as a videophone. A packet sorter622identifies general packets and QoS packets and further identifies the QoS packets to be moving picture and voice RTP packets. The packet sorter622performs packet sorting in a manner similar to the packet sorter612on the base station610side.

A general queue624temporarily accumulates unprioritized general packets every destination IP address ports. A moving picture queue625temporarily accumulates moving picture packets to which QoS is applied, every destination IP address ports.

A voice queue626temporarily accumulates voice packets to which QoS is applied, every destination IP address ports. A packet combiner627passes or combines the temporarily-accumulated packets according to a method to be described later. An interval timer628divides a period T equivalent to the greatest common factor of the voice packet periods U and moving picture packet periods U′ and supplies timing provided for packet combination to the packet combiner627.

A wireless packet transmitter629sends out the packets passed or transmitted through the packet combiner627or the packet combined thereby to the wireless LAN along a period T. Here, the voice and moving pictures differ according to how to see the periods even in the case of the RTP packets as understood from the voice packet generation period600and moving pictures packet generation period601. In the case of the voice of the RTP packets that arrive at the packet sorters612and622, the voice packets arrive at predetermined intervals, but in the case of the moving pictures thereof, a series of RTP packets arrive at intermittent intervals.

In general, the period U′ for the moving picture packet is longer than the period U for the voice packet. In the present embodiment, the QoS queues are sorted into the voice and moving pictures, which are processed according to different methods. When the voice packets first arrive at the packet sorter612in the base station610, the packet sorter612temporarily accumulates the voice packets in queue buffers set every destinations in the voice queue616. Next, when the timing provided to send out each voice queue is issued from the interval timer618, the packet combiner617combines the voice queues for all destinations into one broadcast capsulated packet and sends out it therefrom.

Next, when the moving picture packets arrive at the packet sorter612, the packet sorter612temporarily accumulates the moving picture packets in queue buffers set every destinations in the moving picture queue615. The packet sorter612has already measured, every queue buffers in the moving picture queue615, time intervals that have elapsed since the moving picture packets have been accumulated at the last. When a time interval of a predetermined value or more has elapsed, a dummy queue used as a mark is introduced into its corresponding queue buffer. The dummy buffer is used to recognize the last moving picture packet when the moving picture packets are read from the queue buffers.

When the timing provided to send out each moving picture queue is given from the interval timer618, the packet combiner617reads the moving picture packets from the moving picture queue615every destinations. At this time, the packet combiner617skips reading over the queue buffers at the destinations where no dummy queues are accumulated. When the packet combiner617finds out a dummy packet when it is reading the moving picture packets with respect to one destination, it performs the reading of the motion picture packets for the destination till its discovery, and discards their dummy queues and combines the read moving picture packets into a capsulated packet.

However, when the moving picture packets would overflow a payload of one capsulated packet, they are divided into a plurality of capsulated packets. When allowance is made for the payload of the capsulated packet, the packet combiner617may read and add packageable ones of the general packets for the same destination in the general queue614. The wireless LAN terminal620also results in the flow of processing similar to the base station610.

Here, the packet sorters612and622are similar in packet sorting method toFIGS. 3 and 4illustrative of the first embodiment. While the moving picture packets and voice packets are not sorted in the first embodiment, the present embodiment performs a process in which in the process ofFIG. 3, the pattern matching process for the RTP packets is performed at Step S303(Step S404inFIG. 4) after the processes of Steps S301and S302, and the prioritized QoS packets are further sorted into moving pictures and voice packets.

Described specifically, the packet sorter refers to headers (patterns for a layer5and above) of received packets at Step S303(Step S404inFIG. 4) inFIG. 3and check them against the patterns of the RTP packets registered in the QoS setting table302, thereby further sorting prioritized packets into moving picture packets and voice packets. The present embodiment is similar in other processing to the first embodiment.

In the present embodiment in this manner, the transmission capability of the wireless LAN can be enhanced, and the packets are handled according to the types of voice and moving pictures. It is therefore possible to enhance simultaneous communication capability for real time communication such as a videophone, a television conference that makes use of a wireless LAN, and optimize communication quality.

Seventh Embodiment

A seventh embodiment of the present invention will next be explained. In the seventh embodiment, the period of the CODEC is adjusted according to the number of RTP sessions with which a base station is concerned. A configuration diagram thereof is shown inFIG. 10. Incidentally, a system configuration and configurations of the base station and wireless LAN terminals are basically similar toFIGS. 1 and 2illustrative of the first embodiment.

InFIG. 10, terminals901,902, . . . ,90N on the network side perform real time communication with wireless LAN terminals931,932, . . . ,93N through a network such as Internet, a LAN with a base station920interposed therebetween. While major structure elements are shown in the terminals901, they are common to other terminals902through90N and wireless LAN terminals931,932, . . . ,93N. Incidentally, the terminals901,902, . . . ,90N correspond to the terminals101,102, . . . ,10N ofFIG. 1, the base station920corresponds to the base station120ofFIG. 1, and the wireless LAN terminals931,932, . . . ,93N correspond to the wireless LAN terminals131,132, . . . ,13N ofFIG. 1, respectively. The network110ofFIG. 1is not shown in the drawing. The wireless LAN terminals931,932, . . . ,93N inFIG. 10respectively have functions equivalent to the wireless LAN terminals131,132, . . . ,13N according to the first embodiment.

A CODEC910in the terminal901has an AD (Analog to Digital) conversion function for digitizing an analog signal to generate/compress a periodic digital signal, and a DA (Digital to Analog) conversion function for decompressing/uncompressing the digital signal to take out the analog signal. An RTP packet transmitter/receiver911in the terminal901has the function of generating/transmitting an RTP packet from the signal generated by the CODEC with a payload as the base, and the function of transmitting the received/decoded signal to the CODEC. A CODEC period designation receiver912in the terminal901receives therein a CODEC period designation received from the base station920and makes a period change to the CODEC. A QoS queue921and a QoS number-of-sessions monitor922in the base station920are major components. Of course, the base station920has a function equivalent to the base station120shown inFIG. 1.

The QoS queue921in the base station920is provided in accordance with RTP sessions and temporarily accumulates the RTP packets therein. The QoS number-of-sessions monitor922in the base station920monitors the number of the RTP sessions, generates a signal for extending the period of CODEC when the number of the RTP sessions has reached a predetermined value or more, and shortening the period thereof when it has reached the predetermined value or less, and notifies the RTP sessions to the CODEC period designation receivers912of all the terminated applications. An SNMP or RTCP may be used in this notification.

In the present embodiment, the QoS number-of-sessions monitor922monitors the number of the RTP sessions, and the CODEC period designation receiver912receives therein the CODEC period designation received from the base station920to thereby make the period change to the CODEC. Therefore, when the number of sessions in the real time communication through the base station920increases, the period of the CODEC is extended to enable suppression of the frequency of occurrence of the RTP packets and to make it possible to lessen a problem that due to the difference in throughput between a wired LAN and a wireless LAN, packets are congested at a bridge section of the base station920so that the quality of voice and moving pictures is degraded.

Eighth Embodiment

An eighth embodiment of the present invention will next be explained. In the eighth embodiment, the period of the CODEC is dynamically changed in an IP conversion section or exchanger. A configuration diagram thereof is shown inFIG. 11. Incidentally, a system configuration and configurations of a base station and wireless LAN terminals are basically similar to the first embodiment.

InFIG. 11, external network terminals1001,1002, . . . ,100N such as Internet appliances respectively have CODECs associated with the present system and perform real time communication such as a VoIP (IP phone) or the like. An IP exchanger1010performs a process for switching to real time communication to which the present system relates. An external network1040connects between the external network terminals1001,1002, . . . ,100N and the IP exchanger1010.

LAN terminals1011,1012, . . . ,101N respectively have CODECs associated with the present system and perform real time communication. Wireless LAN base stations1020and1030respectively constitute cells1021and1031. Wireless LAN terminals1022and1032respectively accommodated in the cells1021and1031respectively have CODECs associated with the present system and perform real time communication.

Assuming now that the minimum periods to be expected for the CODECs are respectively defined as S and T, the relation of S<T is established because a small number of the terminals1022are communicating in the case of the cell1021, and a large number of the terminals1032are in communication in the case of the cell1031although the respective wireless LAN terminals1022and1032are performing real time communication. The base station1020and the base station1030respectively notify the CODEC minimum periods S and T to the IP exchanger1010. The IP exchanger1010receives CODEC minimum periods from all of the accommodated wireless LAN base stations1020and1030, applies the longest period thereof (see T in the drawing) and requests all the terminals1022and1032to change the periods of their CODECs.

In the present embodiment, each of the terminals1022and1032is able to determine the CODEC period to be adopted even in the case of the system in which a plurality of the wireless LAN base stations1020and1030have been accommodated. Incidentally, the present embodiment is exactly similar to the first embodiment except for a dynamic change in CODEC period.

Ninth Embodiment

A ninth embodiment of the present invention will next be described. In the ninth embodiment, RTP packets are combined together by an IP switch to suppress the number of packets.FIG. 12shows its configuration. Incidentally, although a system configuration and configurations of wireless LAN terminals are basically similar to the first embodiment, an IP exchanger in the present embodiment has a function equal to the base station of the first embodiment.

InFIG. 12, terminals1101,1102, . . . ,110N perform real time communication with a system through an external network1100such as Internet. A WAN communications unit1111in the IP exchanger (IP switch) of the present system serves as the medium of communications with the external network1100. A QoS determination unit1112extracts RTP packets from packets received by the WAN communications unit1111and sorts them into their corresponding QoS queues set every wireless LAN base stations1120and1130accommodated in the present system.

The QoS determination unit1112refers to a table1113recording the types of the terminals1122and1132connected to the wireless LAN base stations1120and1130accommodated in the present system upon sorting the packets into the QoS queues1114set every base stations1120and1130. The QoS queues1114set every wireless LAN base stations1120and1130accommodated in the system can be provided in plural form.

A packet combiner1115is able to generate capsulated packets every base stations1120and1130held in the system from the QoS queues1114. A LAN communications unit1116has the function of controlling communications between the same LAN communications unit and the wireless LAN base stations1120and1130through a LAN. Incidentally, although not shown inFIG. 12, the IP exchanger1110has the function of transmitting the capsulated packets in matching with the CODEC period in a manner similar to the first embodiment.

The wireless LAN base stations1120and1130respectively form cells1121and1131. Only the terminals1122corresponding to the capsulated packets of the present system are connected to the cell1121. The terminals1132unassociated with the capsulated packets of the present system exist in the cell1131in mixed form. That is, all of the terminals1122in the cell1121respectively have functions equivalent to the wireless LAN terminals131,132, . . . ,13N of the first embodiment. The terminals1132in the cell1131include, in mixed form, terminals A that respectively have functions equivalent to the wireless LAN terminals131,132, . . . ,13N of the first embodiment, and terminals B having no such functions.

The base station1120notifies all of IP addresses of the connected terminals1122being in correspondence with the capsulated packets of the present system, to the accommodated-base station/terminal table1113. When the QoS determination unit1112receives packets for the terminals1122in the cell1121, it sorts the extracted RTP packets into the QoS queues1114, and the corresponding packets are combined together by the packet combiner1115, which in turn is unicasted to the base station1120.

The base station1120allows the capsulated packet to pass through each connection terminal1122. The connection terminal1122judges the capsulated packet to start operating. On the other hand, the base station1130notifies, to the accommodated-base station/terminal table1113, a decision as to whether IP addresses of the terminals1132correspond to the capsulated packets of the present system. The QoS determination unit1112judges into which QoS queue1114the received packets should be sorted with the information of the table1113as the base. When, in this case, the received packets are found to be packets intended for the terminals B, which do not correspond to the capsulated packets of the present system, the QoS determination unit1112transmits the received packets to the LAN communications unit1116as they are.

Thus, the IP exchanger1110combines the RTP packets to allow the number of the packets to be suppressed from the level of the wired LAN. It is therefore possible to lighten the loads on the wireless LAN base stations1120and1130and reduce congestion of the packets, which could happen at bridge portions of the base stations1120and1130due to the difference between the wired and wireless transmission rates.

Tenth Embodiment

A tenth embodiment of the present invention will next be explained. In the tenth embodiment, the transmission of each TCP packet is optimized on a stable basis.FIG. 13is a configuration diagram thereof. Incidentally, although the configurations of a system and a base station according to the present embodiment are similar to the first embodiment, each wireless LAN terminal according to the present embodiment has, as will be described later, the function of suppressing retention of RTP packets in the system in addition to the function of capsulating prioritized packets and the function of transmitting the capsulated packet in matching with a CODEC period, both of which are similar to the first embodiment.

In a wireless LAN terminal1200shown inFIG. 13, which is associated with the present system, an application/CODEC unit1210has the CODEC section and is capable of real time communication. A TCP/UDP unit1220controls a transport layer of an OSI reference model in IP communication. An implement unit1230employed in the present embodiment performs queuing and combining of QoS packets.

A cache table unit1231refers to each transmitted/received TCP packet and a header of its ACK and refers to the difference between the transmit time of the TCP packet and the receive time of the ACK. A use efficiency arithmetic unit1232for computing the use efficiency of a general queue1234is located in the cache table unit1231and calculates RTT (Round Tr IP Time) according to an independent method of the present system. A packet sorter1233sorts the packets supplied from the TCP/UDP unit1220into the general queue1234and one or plural QoS queues1235. A packet combiner1236combines the packets read from the general queue1234and the QoS queue1235to generate a capsulated packet.

A packet reconstructor1237allows a received packet to pass therethrough if it is normal, and extracts a normal packet if it is a capsulated packet. In a wireless packet transmitter/receiver1240, a packet transmitter1241transmits the packet supplied from the packet combiner1236to a wireless LAN, and a packet receiver1242supplies a packet received from the wireless LAN to the packet reconstructor1237.

Since the TCP packets are temporarily accumulated in the general queue1234in principle here, the timing provided to send out each TCP packet is operated so that a variation in RTT increases. It is normally known to implement RTT as the following expression (2). It is however considered that if it is adopted as it is, then the way of RTT being scaled increases, so that the retention of packets occurs in a portion where the packets are supplied from the TCP/UDP unit1220to the packet sorter1233and the capturing of RTP packets from the packet sorter1233to the QoS queue1235is delayed, thereby exerting an adverse effect on communication quality.
RTT=(α×01d_RTT)+((1−α)×New_Round_Time_Sample)  (2)

In the present embodiment, an expression (3) shown below is used. Here, 01d_RTT in the expression (3) indicates a RTT value up to date, New_Round_Time_Sample indicates the time from the transmission of the latest TCP packet to the reception of an ACK, and K and α indicate coefficients, respectively. The speed for reading each packet from the TCP/UDP unit1220is normally controlled in accordance with the RTT value. When the expression (2) is used, such a problem as mentioned above arises.

In the present embodiment, firstly, K in the expression (3) is set to K<1 when the general queue1234is in an empty state, the follow-on TCP packets are extracted earlier than the ideal value, and the general queue1234is made it easy to retain the TCP packets. Thereafter, when the general queue1234has accumulated or retained the TCP packets a predetermined value or more, K is set as K=1, whereas when the general queue1234has dropped below the predetermined value, K is set as K<1. By controlling the value of K in the expression (3) in accordance with the state of the general queue1234in this way, RTT gradually approaches the optimum value relatively smoothly when the general queue1234starts to be supplied with the TCP packets from the empty state. It is therefore possible to suppress the retention of the RTP packets in the TCP/UDP unit1220and stabilize communication quality.
RTT=(α×K×01d_RTT)+((1−α)×New_Round_Time_Sample)  (3)

According to the present invention as described above, received packets are sorted into prioritized packets and packets other than them to make it possible to transmit RTP packets on a priority basis. Further, the prioritized packets are capsulated and the so-capsulated packet is transmitted in matching with a CODEC period, thereby making it possible to enhance the transmission efficiency of packets on a wireless LAN and ensure the quality of real time communication on the wireless LAN.

While the present invention has been described with reference to the illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to those skilled in the art on reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the true scope of the invention.