The third generation mobile communication system is in the second generation of mobile communication technology foundation, has introduced the general grouping wireless service technology and the soft exchange and so on important technical evolution comes. It has many merits, may support the multimedia services, has the mature roaming agreement in the different land wireless service access network, may provide the continual service support for the different user. But it also has the flaw: When data transmission bee value, the transmission speed is low. But has the high transmission band width by 802.11 standard WLAN primarily (802.11 series standards to be able to provide 1~54Mb/s the data transfer rate) the performance. However its shortcoming is also very obvious, each junction point’s coverage area is not big, can only be suitable for the company, the hotel, the airport and so on so-called “the hot spot” the area. Moreover between the different WLAN service provider’s network has not roamed the agreement. This article unifies the third generation mobile communication system and the wireless local area network’s good and bad points supplementary characteristic, proposed that both intercommunication’s plan, will enable the existing wireless local area network resources to play the major role in the future, will cause future communication network to be more perfect.
Based on soft exchange technology 3G core network
the 3G network’s development is carries on the existing network to under the next generation network NGN evolution big background, therefore the 3G network’s evolution should meet the NGN requirement. NGN is may provide the pronunciation, the data and multimedia and so on each kind of service synthesis open network construction, has the following characteristic: Uses the open network construction system, is the service actuation and based on the grouping network.
The soft exchange network’s main idea is the service, the control, the transmission and turning on separates, during various entities carries on the connection and the correspondence through the standard agreement, the entire network divides into four stratification planes: Service application and support level, key-course, transmission level and turning on level. Soft exchange network architecture as shown in Figure 1.
Figure 1 soft exchange network architecture
the 3G core network realizes the plan basic philosophy including the following several aspects. Completes by the enhancement GPRS network to tetherless access network’s turning on and provides the IP channel, causes the intelligence user terminal to carry on the control directly by the key-course soft commutation equipment, simultaneously above the GPRS network the construction one based on the soft exchange’s IP multimedia subsystems, completes to the IP multimedia correspondence controls and service provision. In the core network interior based on the IP transmission, uses the gateway system and traditional PSTN/ISDN/PLMN completely and so on non-IP network carries on the intercommunication and the transformation. Uses based on the soft exchange lamination network architecture system, causes the control and the load bearing separates. This article proposed the core network realizes the plan is according to 3GPP the R5 standard, as shown in Figure 2.
Figure 2 entire IP core network based on soft exchange construction system
Wireless local area network
The wireless local area network (Wireless LAN) is one kind of nimble data transmission system which (Wired LAN) extends from the wired local area network. It uses the radio radio frequency (RF) technology to receive and dispatch the data, usually the computer network’s transmission medium is mainly the copper cable or the fiber optics, the constitution wired local area network. But the wired network needs to receive the wiring in certain situations the limit. The wiring, the re-routing resilience is big; The line easy to damage; In net’s various nodes are intransportable. WLAN can solve the problem which the wired network meets.
WLAN using electromagnetic wave in air transmission and receive data, but does not need the line cable medium. The WLAN data transfer rate already could achieve 11Mb/s now, the transmitting range may far to 20km. It is to the wired company net way one kind of supplement and the expansion, enables on-line computer to have may move to the nature, can solve the network connection problem which conveniently fast the use wired way is not easy to realize. Compares with the wired network, WLAN has the following merit: Installs conveniently, the use is flexible, the economy saves, easy to expand.
in June, 1997, the international electron and electrical engineer organized (i.e. IEEE) to adopt 802.11 standards, it was the IEEE formulation wireless local area network standard, was mainly (PHY) and media key-course (MAC) has carried on the stipulation visit to the network physical level, to the MAC level’s stipulation was key. IEEE 802.11 standard’s agreement structure as shown in Figure 3.
Figure 3 IEEE 802.11 standard agreement structures
3G and WLAN intercommunication
This will be one kind will move the speech network and the WLAN interconnection method. Global only WLAN user indication which and authentication key have using the SIM card and UIM Cary, union migration network perfect authentication, cost system, to WLAN user implementation effective management. When user surfer, may through move the operator existing authentication cost system to carry on the authentication, the user surfer expense may correspond in its handset’s bill, and when has pronunciation inhaling, in the WLAN terminal will have the corresponding prompt, the user may have by the WLAN terminal answers this voice calling or the rejection and so on multiple options. This architecture has two characteristics: User identification and the authentication key carry on the active control using the SIM card or UIM the card WLAN to the WLAN terminal; Using migration speech network data traffic network part.
Figure 4 is based on soft exchange technology 3G and the wireless local area network’s intercommunication schematic diagram. The wireless 3G grouping network or PLMN, SGSN/GGSN will come from RAN through VoIP network connections PSTN through IP the signaling to transmit the multimedia servers/to apply the server (MMCS/MMAS), they have provided with the MSC server same function. The MGS execution passes SG and PSTN or the traditional PLMN signaling. Transmits MG from the RAN media by a RTP package of form through SGSN/GGSN.
Figure 4 3G and WLAN intercommunication schematic diagram
Local area network emulation technology
Because in WLAN and in the 3G fusion plan, ATM faces has the connection, but UDP faces connectionless. Must realize from faces to faces connectionless has the connection transition, must use the local area network emulation technology.
In order to complete the simulation local area network’s function, the ATM local area network emulation technology has joined a protocol function in the ATM network’s adaptive level and between the traditional local area network high-level agreement, is called the local area network emulation level (LAN Emulation Layer). Under this strike uses the 5th kind of ATM adaptive level (AAL5) function, but upward provides the service simulates in the local area network agreement system’s media to visit the (MAC) sublayer. The transmitting end high-level issues the MAC sublayer the data and the control information transforms Cheng Ke by the LE level by the AAL5 recognition form. Comes the transparent transmission through the ATM network, receiving end’s LE level the data conversion MAC service data unit form which receives AAL5 to give high-level. The ATM local area network emulation technology chooses the MAC sublayer contact surface to take the LE level simulation the connection, is because may like this (including traditional local area network and the ATM local area network) provides the unification for each kind of local area network the MAC service connection, simultaneously in interconnection between this on local area network’s may realize by the bridge, realizes the router is simpler. ATM local area network emulation’s agreement stack as shown in Figure 5.
Figure 5 ATM local area network emulation agreement stack
Live transmission agreement
RTP aims at the live transmission agreement which the real-time multi-spot multimedia conferences design, it has provided the end-to-end real-time media (interactive audio frequency and video frequency) transmits the service. RTP is the movement on the UDP transmission level agreement, in order to using UDP multiplexing, inspection and service. However RTP may also uses with other suitable lower level network and the transmission level same place. RTP itself cannot provide any guarantee prompt submission the mechanism, also does not provide other grade of service (QoS) guarantee, but is depends upon the lower level service to complete these tasks. It already does not guarantee the submission, also does not prevent the wrong foreword submission, the supposition subfoundation network is unreliable moreover submits the grouping according to sequence. In the middle of RTP contains atomic number permission receiving end reconstruction transmitting end grouping sequence, but, in the video frequency decoding, the atomic number also possibly uses in determining the grouping the appropriate position, thus does not need to decode the grouping according to sequence. RTP application diagram as shown in Figure 6.
Figure 6 RTP application diagram
Concluding remark
This article proposed one kind unifies 3G and the wireless local area network’s function characteristic, exchanges the plan both. This may cause the two good and bad points to realize supplementary, both has solved the 3G transmission speed low problem, and has solved the wireless local area network cover area small problem, may enable the existing wireless confined network to play the major role in the future.
