HK1119329A - Systems and methods for transporting data across an air interface using reduced address headers - Google Patents

Description

System and method for transmitting data over an air interface with reduced address headers

Technical Field

The present invention relates to wireless systems and more particularly to systems having protocols for data transmission and more particularly to systems and methods for transmitting data over an air interface with reduced address headers.

Technical Field

It has become commonplace to transmit data over an air interface. In most such situations, bandwidth becomes an issue because either a single user (e.g., a PC) may be attempting to move a large data file over a given period of time, or several users are attempting to move smaller files using the same air interface.

Many data transmission protocols are currently used, some related to wire line interconnection (e.g., 802.3 protocols, for example) and some related to air interface transmission (e.g., 802.16, for example). These protocols have several layers including a physical layer and several operational layers. Each such layer is designed to accomplish a certain task and each such layer requires data in a certain format. For example, in addition to sending the payload (typically data), address information must be included as a header so that the payload can be delivered to the appropriate destination. In some cases, it may be necessary to use additional protocols for specific purposes. When this is necessary, additional protocols add overhead (data bits) to the communication payload.

One example of the above problem is when an ethernet header is necessary to be present on a packet to deliver the packet to a particular location within, for example, a local area network. For those portions of the communication channel (e.g., portions of wireline) where bandwidth is substantially unrestricted, overhead from the head is not an issue. However, when communication must traverse the air interface using a dedicated protocol, such as for example the 802.16 protocol, adding an ethernet address in the protocol is a burden to the air interface because it adds bytes (typically 14 bytes). These extra bytes are overhead for the data to be communicated over the air interface and in many cases are superfluous, especially for low data rate transmissions.

One solution to the above problem is to carry the IP on top of the IP convergence sublayer (IPCS), which will then naturally fall at the top of the 802.16 frame in layer 3. The advantage of this approach is that it is very efficient because it is IP on top of IP with no additional overhead, or very little overhead. The downside is that layer3 is designed to carry network routing data as well as data payload, and network administrators do not want to be affected by the overhead of managing a very large amount (in terms of data flow) of layer3 traffic. Such a network structure would be inflexible and difficult to use for practical use.

Disclosure of Invention

The present invention relates to a system and method for utilizing a hybrid protocol layer to transmit data over an air interface to achieve reduced bandwidth. Use is made of the fact that the overhead from e.g. the ethernet protocol is addressing information related to the destination of the packet. This destination information (e.g., ethernet information) may be stripped from transmission before the air interface and re-established after the air interface. In one embodiment, the appropriate Lay2 CS concept is incorporated on top of the 802.16 protocol and still retains the advantages of the Lay2 transparent bridging service layer to the network layer. In one embodiment, the MAC address of the destination is used for the air interface and the ethernet address is re-established and added on the far side of the air interface.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.

Drawings

For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

fig. 1 shows an example of a local area network based system with an air interface according to the present invention;

FIG. 1A illustrates a data packet moving over an air interface from a PC to an access router to a network;

FIG. 1B illustrates a data packet moving from an access router to a PC over an air interface;

FIG. 2 illustrates one embodiment of a method for removing a header from an air interface transmission; and

fig. 3 illustrates one embodiment for adding a header to an air interface transmission.

Detailed Description

Fig. 1 shows a local area network based system 10 having an air interface 11 in accordance with the present invention. In the illustrated system, PC101 is connected to CPE 102 via a high capacity connection 12, which may be a wireline and possibly using the 802.3 protocol, if desired. CPE 102 is connected to base station 103 via air interface 11. The air interface may use, for example, the 802.16 protocol.

The base station 103 is in turn connected to an access router 104 via a high bandwidth connection 13 and the router is connected to a network (e.g. the internet) via a connection 14.

The 802.16 protocol for air interface 11 has two layers (Lay2 and 3) over which data may be sent. Layer two is the main data transfer layer, and layer three handles the information of the main networking. Layer two is designed to handle MAC (or IP address) addresses and not ethernet addresses. Thus, as shown in FIG. 1A, for a packet with an Ethernet header (e.g., header 113), additional data would have to be embedded in packet 110. Thus, as will be seen, the concepts discussed herein will be used to allow data packet 110 from PC101 to traverse air interface 11 as packet 110' without portion 113. On the far side of the air interface a reconstructed portion 113 (called portion 113') belonging to the destination, e.g. access router 104, is added by base station 103 to form a new data packet 110 ". The information carried in the ethernet header 113' of the packet 110 "is the ethernet address of the original destination re-established by the base station 103.

As will be seen, this setup is an efficient use of Lay2 CS, such as the IP-CS MAC used on top of 802.16. Essentially, this is the Lay2.5 protocol used with 802.16. As will be seen, this layer uses additional services, such as a proxy function to be used in conjunction with the IP-CS, and a DHCP snooping function (DHCP snooping function) to supplement the IP-CS that is carrying the IP user application traffic. The combination of these features allows for a transparent bridged Lay2 network to be efficiently represented from the perspective of network administrators and network traffic, and in addition, by effectively having little to no Lay2 overhead in the network, the benefits of a system with very low overhead are created.

Fig. 1B illustrates a data packet 120 moving from access router 104 to PC101 over air interface 11. As will be discussed, in operation, a data packet 120 containing the MAC address 122 of the destination and the data payload 121 has a LAN network address (ethernet header) attached thereto for delivery to the base station 103. The base station 103 then strips the header 123 from the packet 102' to form a packet 120 "in preparation for transmission over the air interface 11. The CPE 102 then adds the ethernet header 123 'of the reconstructed destination (PC 101) to form a packet 120' ".

One embodiment is suitable when the system uses statically configured addresses. In such a system, the access router tells the base station the destination's ethernet address information during the authentication process. The base station then forwards this information (e.g., CPE ID (MAC address) IP, net mask, etc.) to the CPE for temporary storage there. This information then allows the CPE to re-establish the destination ethernet address based on the IP-CS information as part of the MAC address that was not stripped from the packet.

Then, since both the CPE and the base station have the stored ethernet address for a given IP CS address, the ethernet address can be stripped from it and then re-established on the far side of the air interface.

In one embodiment in the case of a dynamically configured address, there is a DHCP helper (DHCP helper) residing in the CPE. A DHCP spoofer (DHCP snooping) is included in the base station. Thus, when the PC initiates a DHCP procedure to obtain the network address for a given session, the CPE and base station will learn and remember the assigned address.

When an APR request (a request to ask where the packet is to be delivered) identifying the PC is found in the base station's look-up table, the base station will respond as if it were the PC destination. The packet is then delivered to the base station using the address of the base station, and the base station forwards the packet to the CPE. The CPE that has the same information in its lookup table as the base station then adds the ethernet address for delivery to the PC.

When the ARP request identifying the destination comes from the PC, the CPE responds with its own MAC address. The PC then sends the packet to the MAC address of the CPE. This eliminates the need for an ethernet header into the base station packet. The base station then adds the appropriate ethernet address because the base station has saved the response from the DHCP server. The packet is then delivered to the router according to the appropriate ethernet destination address.

Fig. 2 illustrates one embodiment 20 of a method for removing a header from an air interface transmission. Process 201 receives a packet for delivery to a destination identified by a header. In some embodiments, the destination header is not piggybacked, as a device (e.g., a base station) will have already told the router to use its address to "know" where to deliver the packet.

The process 202 determines whether the packet is an IP packet. If not, the packet is dropped by process 206. If it is a package, process 203 determines if the package is from its list of service clients. If so, process 204 removes the destination header and process 205 delivers the packet to the air interface.

Fig. 3 shows one embodiment 30 for adding a header to an air interface transmission. Process 301 receives a packet over the air interface. Process 302 determines whether the packet is from a service customer. If not, process 303 discards the packet. If so, process 303 queries (or otherwise obtains) the desired destination and, based on locally obtained information (at the receiving end of the air interface), process 304 delivers the received packet.

From the DHCP snooping point of view, the system actually snoops DHCP packets at both the CPE and the base station so that the bridge knows how to route IP packets. The system spoofs the MAC address of the CPE, which is actually the SSID of the device. The subscriber station identity (subscriber station identity) has the address format of the MAC. In this way, the access router does not know that the bridge is operating in layer3 mode, since the operation appears to be a pure Lay2 operation through the bridge.

In one embodiment, the base station and the listening function of the CPE reside on both the CPE and the base station. In one embodiment, there are two subgroup proxy ARP functions (subgroup proxy arpf action). A proxy ARP function resides at the base station and is a proxy that responds to downlink requests by the access router for the location of destination devices that match a given address. In one embodiment, another proxy ARP function resides on the CPE side and operates to process destination request information from the sending device in accordance with the uplink request.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims (20)

1. A method for delivering data packets over an air interface, the method comprising:

receiving a data packet at a first physical location on one side of the air interface, the packet having a destination at a physical location across the air interface with a private LAN address in addition to its network address;

transmitting the packet over the air interface without the LAN address; and

delivering the transmitted packet to the destination location.

2. The method of claim 1, wherein the packet is received at a second physical location over the air interface, the destination location being determined based at least in part on other information contained within the packet and based at least in part on information stored at the second location.

3. The method of claim 1, wherein the first physical location removes a LAN address from the packet prior to sending the packet over the air interface.

4. The method of claim 3, wherein the second location adds a LAN address of the destination to the packet, the added LAN address derived at least in part from other information contained within the packet and at least in part from information stored at the second location.

5. The method of claim 4, wherein the first and second locations comprise a transmitting and receiving end, respectively, of an air interface bridge, and wherein the air interface is an 802.16 protocol.

6. The method of claim 5, wherein the sending uses at least a portion of the Lay2 protocol of the bridge.

7. A bridge for transmitting data packets over an air interface between devices located on both sides of the interface; the data packet is delivered to a destination location based on an Ethernet address of the destination location; the bridge includes:

means, on the transmit side of the bridge, for transmitting the data packet over the air interface without the Ethernet address attaching to the packet; and

control means on the receiving side of the bridge for controlling the delivery of arriving data packets without an ethernet address attached thereto to an appropriate destination.

8. The bridge of claim 7, wherein the means for sending comprises:

means for removing the Ethernet address from the data packet prior to said transmitting.

9. The bridge of claim 7, wherein the control means comprises:

adding means for adding the ethernet address of the destination location to the received one of the data packets.

10. The bridge of claim 9, wherein the adding means comprises:

at least one look-up table for determining the Ethernet address based on other information contained in the data packet.

11. The bridge of claim 10, wherein the other information is at least in part a unique system identification of the destination location.

12. The bridge of claim 10, wherein the lookup table is structured for a particular session in response to an ARP request from a packet sending location.

13. A method of operating a bridge for transmitting data packets over an air interface between devices located on either side of said interface; the data packet is delivered to a destination location based on an Ethernet address of the destination location; the method comprises the following steps:

transmitting the data packet over the air interface from a transmit side of the bridge without an Ethernet address attached to the packet; and

on the receiving side of the bridge, control is made to deliver arriving packets without an ethernet address attached to them to the appropriate destination.

14. The method of claim 13, wherein the sending comprises:

the ethernet address is removed from the data packet prior to said sending.

15. The method of claim 13, wherein the controlling comprises:

adding the Ethernet address of the destination location to the received one of the data packets.

16. The method of claim 15, wherein the adding comprises:

the ethernet address is determined based on other information contained in the data packet.

17. The method of claim 16, wherein the determining comprises:

using at least one look-up table associated with said other information.

18. The method of claim 17, wherein the other information is at least in part a unique system identification of the destination location.

19. The method of claim 17, wherein the lookup table is constructed for a particular session in response to an ARP request from a packet sending location.

20. The method of claim 13, wherein the sending comprises:

adding address information relating to the destination of the data packet to the data packet instead of the Ethernet address, the added information being determined by the transmit part of the bridge.