KR0119561B1 - Virtual cellular network - Google Patents

Abstract

A virtual cellular network and a communication method thereof are provided, wherein the virtual cellular network includes a plurality of ports, being connected each other by means of port network, for receiving packets which are transmitted from mobile terminals, and a port server for selecting out of one or a plurality of duplex packets which are transmitted from one or more ports included in a temporarily formed virtual cells to transmit the selected packet toward a destination and the mobile terminals, wherein all frequency bands may be utilized by all terminals and the mobile terminals are not limited to one base station in communication by constructing ports around the mobile terminals to receive upward direction signals, and the positioning and installation of the ports are simplified.

Description

Virtual cellular network and its communication method

1 is a schematic block diagram of a conventional cellular communication scheme.

2 is a schematic block diagram of a virtual cellular network in accordance with a preferred embodiment of the present invention.

3 is a flowchart of an uplink packet transmission protocol in a terminal.

4 is a flowchart of a packet processing protocol in a port server.

5 is a flowchart of a downlink packet transfer protocol in a port server.

* Explanation of symbols for main parts of the drawings

Ma ~ Me: Mobile terminal P _A ~ P _N : Port

PN: Port Network PS: Port Server

VC1 ~ VC5: virtual cell

[Field of Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellular communication scheme, and in particular, a virtual having a virtual cell (VC) structure defined as a region of a predetermined size virtually formed around a mobile terminal during a time when a mobile terminal transmits one packet. It relates to a cellular communication network (VCN) and a communication method thereof.

[Private Technology]

The most important is the technology of sharing radio resources in communication methods based on wireless and mobile communication technologies such as indoor and outdoor wireless data communication, vehicles and mobile phones, and future personal communication networks. The method of sharing the radio resources is generally composed of two steps as follows: first, dividing frequency resources by regions, and then adapting a wireless multiple access protocol for each divided frequency band. Is made of. In this regard, the most widely used method is cellular communication.

In the cellular communication method, an area to be serviced is previously divided into cell units, each cell uses a specified frequency band, and adjacent cells use different frequency bands, thereby reducing interference and interference between signals. And, the frequency band used in one cell is reused at a sufficiently long distance (usually adjacent cell in one region), so that it is possible to service a large area with a limited total frequency band. It is an advantage.

A conventional cellular network architecture using seven frequency reuse patterns is shown in FIG.

Each cell C1 to C7 has one base station BS1 to BS7, which is responsible for communication with all mobile terminals MT1 to MT8 present in each cell.

And, all of the base stations BS1 to BS7 are connected to a Mobile Switching Center (MSC) 2 through a wired network L1, and the mobile switch is a public network that is a backbone network (Public Switched Telephone Network (PSTN) 1). ), Etc.

In the conventional cellular communication method, a method of gradually decreasing the size (radius) of a cell is used to increase the number of subscribers per unit area, that is, user capacity. And the introduction of pico cellular technology are under consideration.

However, the method of increasing the user density by reducing the radius of the cell in this way should solve the following problems.

First, as the radius of the cell decreases, the frequency of handover increases and a lot of control signals for processing the handover occur.

The handover is a process in which the mobile station maintains the call connection while the frequency used is changed by the new base station when the mobile station moves to a cell area managed by the other base station while the mobile terminal is connected to one base station. it means.

Secondly, in the existing mobile telecommunication network, the size of the base station was not very important because the cell size was large in number to collection Km. However, as the radius of the cell became smaller, the proper position of the base station was determined according to the shape of the smaller cell. It becomes difficult to select and when installing additional base stations, the interaction with neighboring base stations becomes complicated.

Fourthly, in the conventional cellular communication method described above, even if the throughput is 1 because a multiple access protocol is ideally performed in one cell, the throughput per unit area (normalized to the size of one cell) for the entire frequency band is 1/7 = 0.143. Can not be abnormal (when frequency reuse pattern is 7).

That is, in the conventional frequency reuse communication method, there is no method that can fundamentally solve the limitation of the upper limit of the throughput.

Fifth, in a personal communication network or a mobile phone network, subscribers may be more densely distributed in one area than if they are evenly distributed on the surface. However, in the conventional cellular method, the cell size and boundary are determined based on the average traffic density value. Even if it is, there is a problem that the throughput becomes worse for the temporary change in subscriber distribution.

On the other hand, the research on the wired communication network has been generally studied separately from the wireless mobile communication technology, and much research has not been conducted on their interrelationships.

This is because the logic that the problem of each network is solved in each network has been applied to the background of the research on wired and wireless networks independently.

Accordingly, the interconnector connecting the two networks is designed around the wired network protocol, and the basic assumption is that the wireless network must deliver the complete packet to the wired network side.

The wired network is capable of high-speed transmission of hundreds of Mbps at low cost and low transmission errors due to the development of high speed LAN (Local Area Network) technology and ATM (Asynchronous Transfer Mode) technology. The frequency band is limited, the channel characteristics are irregular, and the transmission error rate is large.

[Summary of invention]

The basic object of the present invention is to provide a new concept of network structure and communication protocol in which wired and wireless networks are efficiently combined in view of the prior art as described above.

****** No manuscript *****

Another object of the present invention is to provide a virtual cellular communication topology (VCN) that can simplify the structure and protocol of the radio portion.

It is still another object of the present invention to provide a VCN capable of increasing subscriber capacity by improving throughput per unit area over the entire frequency band.

It is still another object of the present invention to provide a VCN in which handover processing is simple and base station positioning is easy.

The virtual cellular network (VCN) according to the present invention utilizes the advantages of the wired network to compensate for the shortcomings of the wireless network. The basic concept is to simplify the communication protocol of the wireless channel as much as possible to improve the bandwidth utilization and thereby The traffic increase is accommodated in the wired network connecting the base stations.

This is to use the high speed LAN or MAN (Metropolitan Area Network) as the backbone network of the wireless communication network to simplify the protocol of the Common Air Interface (CAI) by utilizing the bandwidth of the relatively free wired network.

When explaining the VCN according to the present invention compared with the conventional cellular communication method has the following two fundamental differences.

First, in the VCN, all terminals use the entire frequency band allocated to the uplink channel as compared to the frequency reuse pattern of 7 or 9 in the conventional cellular communication network.

This is based on the assumption that when two or more signals are received at the receiving port at the same time, if the strongest signal is stronger than the sum of other interference signals, the signal can be received without error. In this case, since each terminal uses the bandwidth of the entire system, the packet transmission time is reduced as compared with the conventional method using the frequency reuse method, thereby reducing the traffic load per unit area.

In this case, rather than each terminal using a wide frequency band jointly (high speed) to transmit packets, the uplink channel band Bu is divided into a number of (K) subchannels, and the subchannels are randomly selected. It is advantageous to apply a multiple access protocol in each subchannel whose bandwidth is B = Bu / K. In other words, the terminal randomly selects an uplink frequency for each transmission.

This is particularly effective when B << Bc <Bu when the coherence bandwidth of the channel is Bc.

Because in this case there is no need for channel equalization at the receiving port (B <Bc), and moreover, channel fading is independent for each packet transmission due to some sort of random low frequency hopping (SFH). To ensure that

This allows all terminals to transmit packets fairly and prevents terminals with bad channel characteristics from attempting to retransmit continuously in a specific frequency range.

Secondly, the base station (BS), which is located in the center of a cell such as a conventional cellular communication network and allocates a channel to a terminal or manages a handover, is not present in the VCN of the present invention, and in the VCN, a number of functions that are simpler than a conventional base station are simple. Use an array of credit ports, for example an antenna. Each port in the VCN allows any terminal to receive a signal and sends all received packets without error to the port server through the wired network.

By using the arrangement of ports in this way, the port group in the virtual cell basically provides site diversity, and thus, there is an advantage in that it is also strong in multipath fading.

As described above, in VCN, any port in the virtual cell that is temporarily created around the mobile terminal can receive a packet, but there are many advantages, but more than one packet may arrive at the final destination.

This problem is solved by a port server that performs the function of filtering packets transmitted from ports belonging to a certain area.

The size of a virtual cell is defined as the distance that a signal can be received centering on a terminal transmitting a packet. The size of a virtual cell varies depending on the signal power, attenuation pattern, and channel noise.

In order to achieve the above object, the present invention provides a port server for processing a plurality of ports for receiving packets transmitted from a mobile terminal, a wired port network interconnecting them, and all packets transmitted and received through a single port network. It provides a virtual cellular communication network comprising a.

According to still another aspect of the present invention, there is provided a communication method of a virtual cellular communication network in which a plurality of ports are interconnected by a port network and a port server is connected to one end of the port network. In the packet forwarding, *** no document ** transmits a packet from the mobile terminal to each port according to a wireless multiple access protocol, and focuses on the mobile terminal while transmitting one packet from the mobile terminal. Receiving the packet by at least one port included in a virtual cell that is virtually formed, and selecting the best signal among the at least one or a plurality of duplicate packets transmitted to the port server through a port network to a destination. And transmitting the downlink packet from the port server toward the mobile terminal. And designating at least one port for transmitting a packet by the port server, and transmitting the packet to the mobile terminal through the designated port. do.

EXAMPLE

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention in more detail.

2 shows a schematic block diagram of a virtual cellular communication network in accordance with a preferred embodiment of the present invention.

As shown in FIG. 2, in the VCN of the present invention, a plurality of ports P _A -P _N for receiving packets transmitted from a plurality of mobile terminals Ma to Me are mutually connected by a port network PN. One port server (Port Server: PS) that manages a plurality of ports P _A -P _N connected by a port network PN is connected to one end of the port network PN.

The constant port server (PS) is connected to the public network, the backbone network.

FIG. 2 shows the terminals Ma to Me, which are transmitting packets at the same time, especially during the slot time of transmitting one packet.

In addition, the port network (PN) indicates that the bus structure, but, for example, may have a forming or ring structure, they should have a sufficient bandwidth to accommodate the traffic generated in the network area.

In the present invention, each of the ports PA-PN has a much simpler and simpler function than, for example, a conventional base station, and may be configured as, for example, an antenna element.

The virtual cells VC1 to VC5 represented by five circles in FIG. 2 are formed around the mobile terminals Ma to Me and include 14 ports PA-PN therein.

As described above, the virtual cells VC1 to VC5 have a size determined by transmission, attenuation, channel noise, etc., and the boundaries are not predetermined, and the packets are transmitted during the time of transmitting one packet in the mobile terminal. It can be defined as an area that can be received.

In addition, when one or more ports P _A -P _N receive the same packet and transmit the same packet to the port server Ps, the port server PS selects one of duplicate packets and outputs it to the public network as described in detail later. To perform a duplicate packet removal protocol (DRP).

In the present invention, since the DRP is executed in the port server PS instead of the ports P _A -P _N and handover is simplified, the wireless communication protocol of the terminal Ma-Me can be made simple, and as a result, the terminal Has the advantage of reducing power consumption.

On the other hand, all terminals Ma to Me use all frequency bands allocated to the uplink channel when transmitting signals, or divide the uplink all channel bands Bu into a plurality of subchannel bands B / B. A method of randomly selecting one of a plurality of subchannels having a band may be selected.

In the latter case, if the natural band Bc of the channel satisfies the B &lt; Bc &lt; Bu relationship, it is not necessary to perform channel equalization at the receiving ports P _A -P _N (∵B &lt; Bc).

In this case, random low frequency hopping ensures that channel fading is independent for each packet transmission.

[Communication Protocol]

The communication protocol required in the VCN includes the multiple access control (MAC) protocol required for the terminal to access the port as shown in FIG. 3, and the upstream in the port server as shown in FIG. It consists of a packet processing protocol, as shown in FIG. 5 and a downlink packet transfer protocol at the port server, and a multiple access protocol of the port network. This will be described one by one with reference to the accompanying drawings.

A. Uplink Packet Transfer Protocol in Terminal

In the upstream (terminal to port) channel of the VCN, an existing or improved multi-connection protocol can be used, in particular a random access protocol, for example a simple slotted ALOHA protocol. The advantages of the random access protocol are simplicity, flexibility, and not centralized, so you can take advantage of them in a distributed network such as VCN.

Referring to FIG. 3, firstly, each terminal Ma to Me randomly transmits a packet according to the slotted Aloha protocol when a packet is generated (S31). If the entire system frequency band is wide, the entire band is divided into a plurality of subchannels, and each subchannel is randomly selected to transmit a packet (S32). All packets received at the ports P _A to P _N around the terminals Ma to ME are immediately transmitted to the port server PS (S33), and the port server PS sends an acknowledgment signal (ACK). Transmit to the terminal (Ma ~ Me) through the downlink channel. At this time, the terminal waits for a predetermined time (S34), and if the acknowledgment is not received within this waiting time (S35), the terminal proceeds to step S32 and continues to retransmit.

In Figure 2, for example, when *** No **** terminals Mb and Mc transmit packets simultaneously, signals received at ports P _G and P _H will be subject to strong interference. Therefore, the packets from the terminals Mb and Mc are more likely to be sent to the port server PS through the ports PG and PH, respectively. When a packet from a terminal is not captured at any port, the terminal does not receive an acknowledgment signal (Ack). In this case, the terminal attempts to retransmit after a backoff delay.

B. Uplink Packet Transfer Protocol in Port Server

Referring to FIG. 4, when the port server PS receives a new packet transmitted from one terminal, for example (S41), it is determined whether there are duplicate packets (i.e., the same packet is transmitted through multiple paths). Check for a certain time (S42).

Some of these duplicate packets may be packets with no errors and packets that are partially corrupted due to errors in transit.

The port server PS may utilize location diversity by selecting one of these duplicate packets or by combining incomplete packets (S43).

The port server PS sends an acknowledgment signal (ACK) to the terminal every time a successful packet is received (S44), including a subscriber's unique number (ID), a signal input port number, a signal quality and a received time. Create or update a terminal management table (S45).

In FIG. 2, for example, a packet transmitted from the terminal Ma may be transmitted to the port server PS through the four ports PA to PD (duplicated). One of them is selected (S46) and the selected packet is sent to the final destination (S47).

This is defined as duplicated packet elimination protocol (DRP).

The DRP can be largely two methods.

The first method is to ignore all duplicate packets arriving after the port server receives an error free packet.

This simple algorithm minimizes processing delays in the port server.

The second method is that the port server (PS) receives all duplicate packets for a certain period of time, and selects the one with the lowest error rate, for example, the one with the lowest Hamming distance, and sends it to the destination.

In this case, the port server (PS) records the port number where the least error packet is received through each port for each user in the terminal management table, and selects the optimal port to transmit the packet to the terminal when transmitting this information downward. Can be used to

C. Downlink Packet Transfer Protocol in Port Server

In the downlink protocol for transmitting a packet from the port server PS to the terminals Ma to Me, the same virtual cellular concept as in the uplink protocol can be used.

Referring to FIG. 5, when a packet to be sent to the terminal arrives at the port server PS (S51), it is first checked whether the position of the terminal to be received is determined using the terminal management table (S52). The location of the terminal is determined by selecting the port that has the best transmission quality in the uplink transmission as the port closest to the destination terminal.

In order to track the location of the terminal that did not have an uplink transmission, the mobile terminal may periodically transmit a signal indicating its location to the port server PS, or may search through paging.

As a result of the investigation, if the current terminal fails to be located, paging is performed through ports of the entire network managed by the port server PS (S53).

Subsequently, even in the case of paging through the entire network, if the location of the terminal cannot be detected (S54), the terminal reports that the terminal is not in the network (S55).

When the location of the terminal is determined from steps S52 and S54, the port ideally receiving the best uplink signal is ideally designated (S56), and downlink data is transmitted through the designated port (S57).

However, in order to increase the reception rate, it is advantageous to multicast through the ports that exhibited the best characteristics in the uplink transmission and a few peripheral ports instead of steps S56 and S57.

D. Port Network Protocol

The port network PN interconnects the port server PS and all ports P _A to P _N in the network area covered by the port server to carry the up and down data.

Since no direct maintenance data exchange occurs between adjacent ports, the star topology is most suitable as a port network in consideration of packet delay and stability.

However, considering the practical installation aspects, the bus network is suitable for the port network and a ring structure can be used.

If you use the IEEE 820.6 Distributed Queue Dual Bus (DQDB) protocol or a variant of it, one bus is used exclusively by the port server for downlink transmission, and the other bus is used for upstream transmission from the ports to the port server. Can be used.

As described above, the port network can be configured as a high-speed local area network and uses a multiple access protocol suitable for the traffic characteristics between the port and the port server. Since there is no data exchange between adjacent ports, it is desirable to select an efficient protocol suitable for this.

[Pros and Effects]

(1) Increase in subscriber capacity

In the conventional cellular communication method, the MAC protocol is ideally performed in one cell, so that even if the throughput of each cell is 1, the unit ratio (normalized to the size of one cell) and the ratio of the entire system frequency band are 1 /7=0.143 could not be greater than (when the number of frequency reuse patterns is 7), but the fundamental solution to this limit of throughput is to make the number of frequency reuse patterns smaller than 7, with a minimum of 1 do.

That is, all terminals use the same frequency band.

One thing that should be carefully considered in the virtual cellular scheme of the present invention is the problem of indirect signals from other terminals.

This can be compensated with the adoption of the capture function at the time of reception, the reduction of the packet transmission time by 1/7 by using the wide frequency band, and the position diversity gain, and similar number of base stations to the conventional cellular communication method. If you use (port), you can accommodate more subscribers.

(2) acceptance of temporary congestion of subscribers

If the subscribers are distributed in one area on average or temporarily in a personal communication network or mobile phone network, it is difficult to cope efficiently with the existing cellular method, and even though the cell size and boundary are determined based on the average traffic density, With respect to the processing rate becomes poor.

In the VCN of the present invention, all terminals use all frequency bands (that is, by not limiting the frequency bands used in advance), thereby having a better throughput for a dynamically changing user distribution.

That is, in the VCN, a given radio resource can be used to the maximum in the frequency time space [Hz sec ㎡] rather than the frequency time [Hz sec] dimension.

(3) ease of base station positioning

Unlike conventional cellular networks, cell boundaries are not predetermined in VCN. In other words, the cell boundary is defined not at the base station but at the center of the terminal, and the terminal may communicate with any port in the virtual cell.

Thus, VCN has the advantage of providing location diversity and being strong in multipath fading.

By using this approach, VCNs are able to locate ports very freely, and when additional ports are installed to increase subscriber capacity, the interaction with adjacent ports is much simpler than that of conventional cellular base stations. .

(4) Simple Handover Processing Scheme

In VCN, any port around the terminal can receive the packet, and the packet received at the port without error is sent to the port server through the port network. That is, since there is no concept in the VCN that the mobile terminal crosses a predetermined cell boundary, a complicated handover like the conventional cellular method does not occur and a kind of soft handover is achieved.

Therefore, the port of the VCN does not need a complicated function for handover processing, and the port server needs to perform a function corresponding to the handover.

(5) simplification of terminal communication protocol

The VCN minimizes the functions required by the terminal for handover processing, and the power consumption of the terminal can be reduced because the communication protocol of the terminal can be simplified by utilizing the structure of the VCN, especially the port network structure, in the multiple access protocol.

In the above-described embodiment, the structure and communication protocol that can satisfy the basic concept of the VCN according to the present invention has been described by way of example, but many modifications can be made by those skilled in the art without departing from the spirit of the present invention. will be.

Claims (31)

At least one or more ports included in a virtual cell which are interconnected by a port network and temporarily formed around the mobile terminal while transmitting a packet from the mobile terminal and a plurality of ports for receiving a packet transmitted from the mobile terminal. And a port server for selecting one packet among one or a plurality of duplicate packets transmitted from the ports and transmitting the packet to a destination through a public network and transmitting the packet to the mobile terminal through the port. Cellular network. The virtual cellular communication network of claim 1, wherein the mobile station transmits a packet from a terminal using a full frequency band allocated to an uplink channel in a port direction. The virtual cellular terminal according to claim 1, wherein the mobile terminal divides a full frequency band allocated to an uplink channel in a port direction from a terminal and transmits a packet using one of a plurality of divided subchannels. communications network. 4. The virtual cellular communication network according to claim 3, wherein the relationship B &lt; Bc &lt; Bu is satisfied when Bu is the uplink full channel band, B is the subchannel band, and Bc is the natural band of the channel. 4. The virtual cellular network of claim 3, wherein the mobile terminal randomly selects a subchannel. The virtual cellular communication network of claim 1, wherein the port network has a bus structure or a molded structure. 2. The virtual cellular network of claim 1, wherein the port server selects an error-free first received packet among the plurality of duplicate packets and ignores duplicate packets received thereafter. The virtual cellular communication network of claim 1, wherein the port server selects a packet having the lowest error rate among the plurality of redundant packets received for a predetermined time. 9. The virtual cellular network according to claim 8, wherein the packet having the smallest error rate is determined by a Hamming distance. 9. The virtual cellular communication network of claim 8, wherein the port server includes a terminal management table including port information on which the least error packet is received for each terminal. 11. The virtual cellular network according to claim 10, wherein the terminal management table includes at least a user unique number, a packet receiving port number, a packet signal quality and a reception time. The method of claim 1, wherein the communication protocol for accessing any port in the virtual cell from the mobile terminal is configured with a wireless multiple access protocol, the communication protocol of the port network is configured with a multiple access protocol. communications network. 13. The virtual cellular network of claim 12 wherein the multiple access protocol is a random access protocol. The virtual cellular network of claim 1, wherein the port server transmits a packet to the mobile terminal through a port that has received the best packet. 2. The virtual cellular network according to claim 1, wherein the port server transmits the packet to the mobile terminal in a multicasting manner through a port that has received the best packet and a predetermined port around the port. 2. The virtual cellular communication network of claim 1, wherein the port server selects in a location diversity manner by using duplicate packets received through various ports. 7. The system of claim 6, wherein the bus is used for a first bus exclusively used by the port server for downlink transmission of packets from the port server to the port, and for upstream transmission of packets from the ports to the port server. And a second bus that is configured to be a virtual cellular communication network. 18. The virtual cellular communication network according to any one of claims 1 to 17, wherein each port consists of an antenna. A plurality of ports for receiving a packet transmitted from a mobile terminal, a port network for interconnecting the plurality of ports, and a virtual cell formed virtually while transmitting a packet about the mobile terminal. Port server for selecting the best signal among at least one packet received from the at least one port through the port network to the destination, and transmitting the packet through at least one port to the mobile terminal through the port network. Virtual cellular network, characterized in that consisting of. In a communication method of a virtual cellular communication network in which a plurality of ports are interconnected by a port network and a port subsidiary is connected to one end of the port network, uplink packet transmission from a mobile terminal to a port direction is wirelessly connected from the mobile terminal. Transmitting one packet to each port according to a protocol; and at least one port included in a virtual cell formed virtually around the mobile terminal while transmitting one packet from the mobile terminal. And selecting the best signal among the at least one or a plurality of duplicate packets transmitted to the port server through a port network, and transmitting the selected signal to a destination, the downward direction of the mobile terminal from the port server. Packet transmission is for transmitting a packet by the port server. Even if the communication method of the communication network, characterized in that the virtual cell consisting of a step of specifying a port and, transmitting the packet to the MS via the specified port. 21. The method of claim 20, wherein when the uplink packet is transmitted, the mobile station transmits a packet using a full frequency band allocated to an uplink channel. The method of claim 20, wherein the mobile station transmits the packet using any one of a plurality of divided subchannels when the uplink packet is transmitted. 23. The method of claim 22, wherein the selection of any one of the plurality of subchannels is made by a multiple access protocol. 24. The method of claim 23, wherein the multiple access protocol is a random access protocol. 21. The method of claim 20, wherein selecting the best signal among the duplicated packets comprises selecting a packet having the lowest error rate among the plurality of duplicated packets received for a predetermined time. 21. The method of claim 20, wherein the specifying of the packet transmission port designates a port that received the best packet during uplink packet transmission. 21. The communication method according to claim 20, wherein the step of designating a packet transmission port designates a port that received the best packet during uplink packet transmission and a predetermined port around the port. 21. The communication method according to claim 20, wherein the packet transmission from the designated port to the mobile terminal is multicasting through a plurality of ports. 21. The method of claim 20, wherein the packet transmission from the port network to the port server is performed by a slotted Aloha protocol. 21. The method of claim 20, wherein the step of selecting the best signal among the duplicated packets selects the first received packet without error and ignores the duplicated packets received thereafter. 21. The method of claim 20, further comprising determining a location of a terminal to which the downlink packet is to be transmitted, and if the location of the terminal is not determined, paging through all ports. Communication method.