US20080052548A1 - System for low power operation of wireless lan interfaces - Google Patents

Images

Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/02—Power saving arrangements
  • H04W52/0209—Power saving arrangements in terminal devices
  • H04W52/0212—Power saving arrangements in terminal devices managed by the network, e.g. network or access point is leader and terminal is follower
  • H04W52/0216—Power saving arrangements in terminal devices managed by the network, e.g. network or access point is leader and terminal is follower using a pre-established activity schedule, e.g. traffic indication frame
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F15/00—Digital computers in general; Data processing equipment in general
  • G06F15/16—Combinations of two or more digital computers each having at least an arithmetic unit, a program unit and a register, e.g. for a simultaneous processing of several programs
  • G06F15/177—Initialisation or configuration control
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
  • G06F1/26—Power supply means, e.g. regulation thereof
  • G06F1/32—Means for saving power
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
  • G06F1/26—Power supply means, e.g. regulation thereof
  • G06F1/32—Means for saving power
  • G06F1/3203—Power management, i.e. event-based initiation of a power-saving mode
  • G06F1/3206—Monitoring of events, devices or parameters that trigger a change in power modality
  • G06F1/3209—Monitoring remote activity, e.g. over telephone lines or network connections
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L67/00—Network arrangements or protocols for supporting network services or applications
  • H04L67/01—Protocols
  • H04L67/02—Protocols based on web technology, e.g. hypertext transfer protocol [HTTP]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L67/00—Network arrangements or protocols for supporting network services or applications
  • H04L67/50—Network services
  • H04L67/56—Provisioning of proxy services
  • H04L67/568—Storing data temporarily at an intermediate stage, e.g. caching
  • H04L67/5681—Pre-fetching or pre-delivering data based on network characteristics
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L67/00—Network arrangements or protocols for supporting network services or applications
  • H04L67/50—Network services
  • H04L67/56—Provisioning of proxy services
  • H04L67/568—Storing data temporarily at an intermediate stage, e.g. caching
  • H04L67/5682—Policies or rules for updating, deleting or replacing the stored data
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L67/00—Network arrangements or protocols for supporting network services or applications
  • H04L67/50—Network services
  • H04L67/60—Scheduling or organising the servicing of application requests, e.g. requests for application data transmissions using the analysis and optimisation of the required network resources
  • H04L67/62—Establishing a time schedule for servicing the requests
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
  • H04L69/16—Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
  • H04L69/163—In-band adaptation of TCP data exchange; In-band control procedures
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
  • H04L69/16—Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
  • H04L69/165—Combined use of TCP and UDP protocols; selection criteria therefor
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/02—Power saving arrangements
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W84/00—Network topologies
  • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
  • H04W84/10—Small scale networks; Flat hierarchical networks
  • H04W84/12—WLAN [Wireless Local Area Networks]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L67/00—Network arrangements or protocols for supporting network services or applications
  • H04L67/50—Network services
  • H04L67/56—Provisioning of proxy services
  • H04L67/59—Providing operational support to end devices by off-loading in the network or by emulation, e.g. when they are unavailable
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
  • H04L69/16—Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
  • Y02D30/00—Reducing energy consumption in communication networks
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
  • Y02D30/00—Reducing energy consumption in communication networks
  • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

• the invention disclosed broadly relates to the field of wireless communications, and more particularly relates to the field of power management in wireless local area networks (LANs).
• LANs wireless local area networks
• FIG. 1 there is shown an example of a known wireless LAN system 100 comprising a wired LAN 120 which comprises a LAN server 124 and a wired Client 122 , both coupled to the LAN by a wireline bus 128 .
• the system further comprises a plurality of access points (APs) 126 which are similar to base stations in a cellular system.
• Wireless Client Units 132 typically communicate with the access points 126 over the air in an unlicensed frequency such as the 2.4 GHz ISM (Industrial, Scientific and Medical) band.
• APs 126 are connected to an Ethernet hub or LAN server and transmit radio frequency signals over an area of up to a thousand feet which can penetrate walls and other non-metal barriers.
• Roaming users can be handed off from one access point 126 to another as in a cellular mobile phone system.
• Laptops use wireless modems that plug into an existing Ethernet interface or that are self-contained on PC cards, while stand-alone desktops and servers use plug-in cards.
• Wireless units Power consumption by mobile stations (wireless units) is a significant problem because these units are generally battery-powered, and to support wireless communication requires a level of power consumption that significantly reduces battery life, See for example E. Shih et al, “Wake on Wireless: An Event Driven Energy Saving Strategy for Battery Operated Devices, ” MobiCom 2002.
• WLAN Clients or STAs in 802.11 parlance
• an access point (AP) 126 connects the Wireless Client Units 132 to another network medium, typically a wired Ethernet medium.
• the role of the APs 126 is to synchronize the Wireless Client Units 132 on a common time base and to buffer packets on behalf of the Wireless Clients 132 as well as coordinate delivery of the packets to the Clients 132 . Synchronization is maintained by a beacon signal which is launched by the AP 126 typically every 102.4 ms.
• the AP 126 provides support for the Clients 132 operating in one of two power modes, namely the Constant Awake Mode (CAM) and the Power Save (PS) mode.
• CAM Constant Awake Mode
• PS Power Save
• Clients 132 are registered with the AP 126 as constantly being in the “Awake” state which means they must always be monitoring the wireless medium. Accordingly, the AP 126 may send packets to the Client 132 at any given time. Since the receiver of Client unit 132 is always on in the Constant Awake Mode, this mode also consumes the most power.
• Clients 132 are registered with the AP 126 as being in the “Doze” state between beacon signals and as “waking up” temporarily to receive selected beacon signals.
• the AP 126 must buffer packets destined for Clients 132 that are registered as being in the PS mode.
• the AP 126 informs Clients in PS mode if there are packets queued up at the AP 126 by including a Traffic Indication Map in the beacon signals that the Client 132 is expected to receive.
• the Client 132 in PS mode will poll the AP 126 to retrieve the queued-up packets.
• Clients 132 operating in the PS mode may have significantly lower power consumption. Clients 132 can further reduce their power consumption by skipping beacon signals. Clients 132 may do so after first informing the AP 126 of their intention by passing a parameter known as the ListenInterval to the AP 126 .
• the power consumption, Pdoze, in the wireless interface when the Client 132 is in the Doze state is much less than power consumption when the Client 132 is in the Awake state, or Pawake.
• the ListenInterval beyond 10 which increases Tdoze beyond 1 second, the power consumption of the Client 132 may be reduced by almost two orders of magnitude below the CAM mode.
• TCP Transfer Control Protocol/Internet Protocol
• IP Transfer Control Protocol/Internet Protocol
• TCP/IP Transfer Control Protocol/Internet Protocol
• An endpoint is defined as an IP address and TCP port number pair.
• An association of two distinct endpoints is called a TCP connection and the TCP protocol defines the mechanisms for establishing connections, for reliable data delivery, and for terminating connections.
• the TCP is a symmetric protocol (i.e., the same connection guarantees reliable data delivery in both directions; either one of the two endpoints can initiate the establishment or termination of a connection; and the protocol provides for simultaneous open and close).
• client and ‘server,’ respectively, and refer to the data flow from the server to the client only.
• Reliable data packet delivery is accomplished via two means.
• the client must acknowledge each DATA packet it receives from the server, typically one ACK packet (used to acknowledge the error-free receipt of transmitted data) for every two DATA packets.
• the server will only send a limited number of DATA packets while allowing for the ACK packet(s) to be received later.
• the maximum number of outstanding, i.e. non-ACKed, data packets expands according to a congestion window size (CWND) algorithm, as explained below. This algorithm, however, restarts for every new network connection that is established at the TCP level.
• FTP File Transfer Protocol
• the client may issue the command “get ⁇ file_name>” on the command connection, the first connection established between the FTP client and server.
• a second TCP connection called the data connection, is established between the client and the FTP server, and upon receipt of the entire file, the data TCP connection is torn down.
• the FTP service is configured to use passive-mode, (as most anonymous FTP servers and clients, such as Netscape, are configured today), the following describes the dynamics of the packet transfer between the client and the server as well as the CWND algorithm during the lifetime of the connection.
• SYN synchronization
• the server must respond immediately with a SYN packet, which must also acknowledge (ACK) the receipt of the client SYN packet.
• SYN/ACK packet This server packet is called a SYN/ACK packet, because of its dual role.
• the server initializes its CWND variable to a value of one.
• the client acknowledges the SYN/ACK packet immediately, by sending an ACK packet.
• all ACK packets are cumulative.
• the server increases its CWND by one, as specified by the CWND algorithm.
• the server will send two data packets (if the requested file is large enough).
• the server increases its CWND by one for every ACK it receives, up to a very large limit, and it sends the maximum number of packets allowed by the current CWND, the last ACK, and the file size; the client sends an ACK packet for every two data packets it receives, or after a system-dependent timeout expires (typically 100 ms), if there is any unacknowledged data received.
• the CWND algorithm is substantially more complex, due to its handling of extraordinary events, such as packet loss and reorder or idle timeout expirations, when CWND is reduced, such as halved or reset to one, and its upper limit reset to a lower limit, such as its value before the event.
• extraordinary events such as packet loss and reorder or idle timeout expirations
• CWND is reduced, such as halved or reset to one
• upper limit reset to a lower limit
• the Client 132 is slow to receive the SYN/ACK packet, its transmission of the first ACK packet will be delayed. And then if the Client 132 is slow to receive the first two DATA packets it will also be slow to acknowledge them. As the CWND grows larger, and the instantaneous throughput increases, the AP 126 is queuing up an increasing number of DATA packets (up to the CWND number of packets). This is occurring while the Client 132 is in the Doze state. The Client 132 may then fetch packets very rapidly after the next beacon signal it receives (when it is in the Awake state).
• the maximum throughput of 50 maximum sized DATA frames per 102.4 ms beacon is based on measurements performed with an 802.11b wireless LAN client operating in the CAM mode and corresponds to a maximum throughput of 700 kilobytes per second (kByte/s), or about half the speed of the wireless interface itself.
• the inefficiency is mainly due to 802.11b protocol overhead. TCP/IP frame overhead also contributes.
• Ttimeout is reset to its original value, say 100 ms, after a DATA packet has been either transmitted or received.
• the problem with utilizing the CAM mode is an increased power consumption if the Client-server bandwidth is smaller than the wireless bandwidth. As long as there are DATA packets being received, or sent, the Client 132 will remain in the CAM mode for another 100 ms. Therefore, if the overall throughput is slow, the Client 132 will spend excess time in the CAM mode waiting for DATA packets to arrive at the AP 126 . As the Client-Server bandwidth decreases, the power efficiency decreases too.
• Typical Client-Server throughput on the world-wide web (WWW) is in the range of 25-150 kBytes/second depending on the particular server and its load and on the Client's browser. This throughput may be measured by a web sniffer (software and/or hardware that analyzes traffic and detects bottlenecks and problems in a network) such as IBM's PageDetailer.
• speculative prefetching See X. Chen, X. Zhang, “A popularity-based prediction model for web prefetching”, IEEE Computer, March 2003, for a discussion of prefetching.
• the efficiency of speculative prefetching is not reliable, or predictable, on a per client basis.
• Speculative prefetching works best in proxy servers which host thousands of clients, and which see very high throughputs. Prefetching proxies also constantly have to revew pages as they time out, and therefore generate a significant amount of network traffic. It is therefore also beneficial for overall network performance if there are not too many of such proxies.
• proxy servers to enhance and support the capabilities of clients. See D. Gourley, B. Totty, “HTTP: The definitive guide”, O'Reilly, 2002, for a good survey of proxy servers and how they function. Proxy servers have been developed for many purposes. Probably, the most well known types of proxy servers are the web cache proxy server and the security firewall proxy server. Other interesting types include proxies for transcoding content to better suit the capabilities of a certain device (such as a PDA), and filtering proxies for blocking access to inappropriate web sites. There are, however, no proxy servers that optimize for power consumption in the clients.
• a method for conserving power in the client module includes: configuring a wireless interface to promote energy savings when using a proxy server; buffering data destined for the wireless client unit at the proxy server; and releasing the data to the client module responsive to the occurrence of at least one specified condition that promotes energy savings.
• FIG. 1 is an illustration of a prior art wireless LAN system.
• FIG. 2 shows a representation of a wireless LAN environment wherein a system in accordance with the invention can be advantageously used.
• FIG. 3 shows a more detailed representation of a portion of the network shown in FIG. 2 .
• FIG. 4 shows a graphical representation of power consumption using a direct scheme, according to the prior art, and the proxy scheme, according to an embodiment of the invention.
• FIG. 5 shows a flowchart of Web page retrieval using a Proxy Server, according to an embodiment of the invention.
• FIG. 6 shows a simplified block diagram of an Application Proxy Server, according to an embodiment of the invention.
• FIG. 7 shows a block diagram representation of a wireless client, according to an embodiment of the invention.
• the system 200 comprises a plurality of wireless client units such as Wireless Client 202 . These can be laptop computers, personal digital assistants or other wireless communication devices, wherein battery life is an important consideration.
• the Wireless Client 202 is connected to an Intranet 214 via an Access Point (AP) 206 that comprises a wireless transceiver for providing wireless communication with a Client 202 .
• the AP 206 is often connected to the Intranet 214 through a Multiport Ethernet Switch 205 as shown in FIG. 2 .
• an Application Proxy Server 204 is also connected to the Intranet 214 and to the AP 206 through the Multiport Ethernet Switch 205 .
• the Intranet 214 is connected to the Internet 210 via a Gateway 208 . Also connected to the Internet 210 is a Server 212 (called an Origin Server herein).
• the network 200 uses the TCP/IP protocol to exchange packets.
• FIG. 3 there is shown an illustration of a more detailed block diagram of the network 200 , according to an embodiment of the invention.
• the Intranet 214 is shown as a Wired LAN 306 such as the one discussed with respect to FIG. 1 except that it now includes a plurality of application Proxy Servers 204 each connected to the AP 206 and the rest of the Wired LAN 306 through Multiport Ethernet Switches 205 .
• the Wireless Clients 202 are also different from those shown in FIG. 1 in that they are adapted to use the services of the Proxy Servers 204 .
• the Proxy Server scheme works by prefetching application data from the Origin Server 212 . This causes data to accumulate in the Proxy Server 204 until the wireless Client 202 is able to retrieve the data and until the Proxy Server 204 releases the data. In this fashion, the Client 202 is not required to communicate with the Origin Server 212 in the CAM mode, as now this task is handled by the Proxy Server 204 .
• the Client 202 still has to wait for data packets from the Proxy Server 204 in the CAM mode. But since the Client-Proxy bandwidth (e.g. 750 kBytes/s) is much greater than the Client-Origin Server bandwidth (e.g. 25-150 kBytes/s), the Client 202 may retrieve data packets about 5-30 times faster from the Proxy Server 204 , and therefore spend up to 5-30 times less time in the CAM mode, thereby reducing energy consumption.
• the Client-Proxy bandwidth e.g. 750 kBytes/s
• the Client-Origin Server bandwidth e.g. 25-150 kBytes/s
• the Client 202 may adjust its own Ttimeout to be very small since it knows that the response time of the Client-Proxy connection is very high, due to the high Client-Proxy bandwidth.
• the only factor that may really impact the response time is the wireless network itself, e.g. due to contention or data loss. Communicating via the AP 206 and the Proxy Server 204 will be fast in comparison to communicating directly with the Origin Server 212 .
• Ttimeout 25 ms. The net effect of all this is that the Client 202 may significantly reduce energy consumption while in the CAM mode.
• the Client 202 is configured to detect the presence of the Proxy Server 204 and to adjust its Ttimeout according to whether the Proxy Server 204 is available to cache messages or not.
• the Proxy Server 204 operates at the application level.
• a web browser application is used. So in this case, the Proxy Server 204 is a web proxy which uses HyperText Transfer Protocol (HTTP) to retrieve web pages and objects from the Origin Server 212 .
• HTTP HyperText Transfer Protocol
• the Client 202 uses HTTP to retrieve web pages and objects from the Proxy Server 204 .
• FIG. 4 we see two charts 410 and 420 , illustrating the dynamic power consumption (Power) in the Wireless Client's 202 WLAN interface and the number of accumulated DATA packets, NDATA, in two different systems: 1) when the Client 202 is connected directly to the Origin Server 212 , as shown in the Direct scheme 410 ; and 2) when the Client 202 is making use of the Proxy scheme 420 .
• SYN and FIN represent the initial Client 202 TCP connection request packet and the final Client 202 TCP connection packet, respectively.
• the remaining “down” arrows ( ⁇ ) indicate the arrival of DATA packets a) at the Access Point 206 and b) at the Proxy Server 204 .
• the Proxy Server 204 accumulates packets at whatever speed they may arrive at the Proxy Server 204 .
• the Client 202 is in the Doze state saving energy.
• the Web Proxy Server helps reduce the Client 202 power consumption in at least two ways. First, by splitting the TCP connection between client and server into two separate connections, Client-Proxy and Proxy-Server. This split buffers the Client 202 from the negative effects that wide-area network conditions (e.g., limited bandwidth, high latency, packet loss) have on the packet dynamics and its impact on the Ttimeout selection.
• the benefits of splitting the TCP connections at the Proxy Server 204 apply to any TCP traffic that is mostly unidirectional, towards the Client 202 .
• the second benefit is specific to Web content and it is illustrated in FIG. 5 which shows a flowchart 500 detailing the process of retrieving and releasing a web page. More specifically, the second benefit stems from the way web pages are constructed, with a main page which may include several other objects embedded in this page.
• the process begins at step 510 with the receipt of an HTTP request from the Client 202 which wakes up the main thread, ProxyMain(*Object).
• ProxyMain(*Object) In case of the initial HTTP request, the Web Proxy Server spawns the GetWebObject(*Object) thread in step 512 which fetches the object from the Origin Server 212 .
• *Object is a pointer to the HTTP request header string.
• the header includes the Origin Server 212 name, the path name of the object/page, and the cookie, among other things.
• step 514 it is first determined in step 514 if the object has already been fetched and therefore present in the cache. If the object is absent in the cache then in step 516 the GetWebObject( ) thread is woken up. If the object is present in the cache then in step 518 the ReleaseObject(*Object) thread is spawned, releasing the object to the Client 202 . The thread is then put into a wait state in step 520 .
• Step 530 is the GetWebObject(*Object) thread. This thread fetches the object from the Origin Server 212 in step 532 , saves it in cache in step 534 and then spawns the ReleaseObject(*Object) in step 536 to release the object to the Client 202 .
• step 542 the next object is fetched from the Origin Server 212 and then saved in cache in step 544 .
• step 540 If the current object is parseable, execution returns to step 540 . If the current object is not parseable, the object count is decremented by one in step 546 . If there are more objects to prefetch, then execution returns to step 542 . When all objects have been prefetched, the thread is put into a wait state in step 538 .
• Step 560 is the ReleaseObject(*Object) thread which releases the object to the Client 202 in step 562 and then terminates the thread in step 564 .
• ReleaseObject( ) threads are always spawned and immediately terminated upon complete transfer of an object. This enables the Proxy Server 204 to accept multiple successive Client 202 requests, i.e. pipelined requests, in step 510 .
• the ReleaseObject( ) threads synchronize with each other during servicing of pipelined requests to conform to the HTTP protocol specifications.
• step 532 assumes that the object has not already been received in an earlier request. If the object is already in cache, then step 532 may simply fetch the object from cache, skip step 534 and jump to step 536 .
• the flowchart 500 shown in FIG. 5 accounts for releasing web objects based on the condition of receiving the entire object.
• web data may be released on other conditions as well.
• another condition could be to release web data based on exceeding a certain amount of buffer space.
• Yet another condition could be to release web data based on a timeout.
• the Proxy Server 204 could start releasing web data before it has received an entire object.
• the number of embedded objects may vary from a few to more than one hundred and depends on the Web page content and the Web design tool(s) used.
• the Proxy Server 204 may attempt to emulate some of the client actions with respect to parsing the main page and requesting the embedded objects. For example, it is up to the particular implementation of a web browser in which order embedded objects are requested. The same holds true for objects manifesting themselves as a result of executing other embedded objects. Since, in principle, the Proxy Server 204 may know which web browser a Client 202 is using, the Proxy Server 204 can adjust its prefetching policy accordingly to better match the subsequent sequence of requests from the Client 202 .
• the Client 202 may remain in the Doze state for a longer period and occasionally wake up to determine if there are packets queued up at the Proxy Server 204 .
• the Client 202 stays in the Awake state until it has received all currently released objects from the Proxy Server 204 and that this time interval (Tawake) is significantly shorter than in the non-proxy configuration, as the embedded objects are served from the local Proxy Server 204 cache.
• the Client 202 will return to the Doze state soon after the last object is retrieved, since the Client 202 can be configured with a low Ttimeout value as packet transfers occur across the low-latency Client-Proxy connection.
• the Client 202 must be configured (programmed or wired) to detect the presence of the Web Proxy. This is important because the Power Management (PM) mechanism in the Client 202 will depend upon the expectations to the Client-Server latency and server properties as explained earlier. This may be done as follows.
• a ProxySniffer( ) daemon is using a UDP port. Occasionally, it will broadcast a sniff packet on an agreed upon UDP port and then wait for a response. The sniff packet may contain information about the browser's capabilities and configuration.
• an Alert( ) daemon is listening on the agreed upon UDP port. When it detects the sniffpacket from the Client 202 it responds with its IP address, TCP port and capabilities.
• the Client 202 then configures the Web browser application to use the Proxy Server 204 .
• the Client 202 selects a suitable Power Management (PM) scheme for the wireless LAN interface.
• PM Power Management
• Ttimeout 25 ms in the MAC network layer.
• the Client 202 must be able to share Proxy Server 204 information with the MAC. This is described later. Note that to prevent the sniff packet from propagating to proxies belonging to other APs, each Proxy Server 204 should be on a different IP subnet, since broadcast packets do not propagate across subnets.
• the Client 202 should also be able to determine if there are any application network sessions or not.
• application session context is only known within each application.
• a more suitable PM scheme may be selected.
• the WLAN interface may be completely shut down, and then started up again when the user clicks on a hyperlink.
• the following discussion describes how to retrieve the application session context and how to transmit the session and Proxy contexts to the MAC layer and how to reflect the Proxy context in the network settings of the Web browser.
• a SessionContext( ) module hooks into the TCP protocol layer where it intercepts communication on all the relevant ports, to determine when a connection is opened and closed, by intercepting all communication with the IP network layer.
• SessionContext( ) also needs to know which application is associated with each port which may be retrieved from known system configuration files or databases.
• Those skilled in the art of network programming will know how to implement the SessionContext( ) module.
• tools for retrieving network context are commercially available. For example, the network context can be made available at the user level on a Linux client using shell commands such as ‘netstat -t’, which lists all the TCP connections of the client, their state, and receive and send queue sizes.
• the IP address of the Proxy Server 204 in the Web browser is known to anyone skilled in the art of systems programming. For example, under Microsoft WindowsTM it is a matter of updating the particular key in the Windows Registry which holds the address of a Proxy Server 204 . Also the particular key that instructs the browser to use a Proxy Server 204 in the first place must be enabled, or disabled if the Proxy Server 204 disappears. Finally, the Web Browser's configuration utility must be toggled in order to detect the modifications made to the Windows Registry keys.
• NAT Network Address Translation
• Web Proxy could also be an Email Proxy or any other network application Proxy.
• the Proxy 204 could also be integrated with the Access Point 206 , and that the Proxy Server 204 could be located anywhere else on the Intranet 214 , or even on the Internet 210 . What is important for the sake of reducing power is that there is a high-speed connection between the Wireless Client 202 and the Proxy Server 204 . Therefore, the closer to the Access Point 206 the Proxy Server 204 is, the higher is the connection bandwidth between the Client 202 and the Proxy Server 204 .
• the Proxy Server 204 comprises a Buffer 600 for storing data (or other information) destined for a Client unit 202 .
• the Buffer 600 is a part of the system memory (RAM) of the Proxy Server 204 , controlled by a Buffer Control Program 602 .
• a Client Alert Program 608 informs clients of the IP address and other capabilities of the Proxy Server 204 .
• the Buffer Control Program 602 and the Client Alert Program 608 can be implemented as software which executes on a Processor 604 .
• An Input/Output (IO) Interface 606 will enable communication with clients and other information processing systems.
• the Proxy Server 204 operates at the network application level, or more specifically at the layer 5 and above the Open System Interconnection (OSI) ISO standard.
• OSI Open System Interconnection
• the Proxy Server 204 is a Web Proxy which uses HyperText Transfer Protocol (HTTP) to retrieve web pages and objects from the Origin Server 212 .
• HTTP HyperText Transfer Protocol
• the Client 202 uses HTTP to retrieve Web pages and objects from the Proxy Server 204 .
• the Proxy Server 204 comprises software configured to delay processesing at least some of the data buffered for a client for an amount of time greater than zero based on detected operating parameters of the client.
• the operating parameters comprise the type of device that the client is such as a mobile telephone or a wireless laptop or palmtop or the operating system used.
• the Proxy Server 204 can detect these operating parameters by analyzing signals received from the Client 202 .
• the parameters can be expressly stated in for example metadata or can be inferred from the type of signal received (e.g., the protocol used).
• the Proxy Server 204 can be programmed to adjust the processing delay by predetermined amounts of time according to the detected parameters.
• FIG. 7 shows how a Wireless Client 202 may be configured according to an embodiment of the invention.
• a Wireless Client 202 may be configured with components to include a radio-frequency (RF) Transceiver 702 , a Processor 704 , a Proxy Server Detector Program 706 , a Proxy Configuration Program 708 , and a Client Configuration Program 710 .
• RF radio-frequency
• a Battery 712 will also be part of the configuration.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Theoretical Computer Science (AREA)
• Computer Security & Cryptography (AREA)
• Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Computer Hardware Design (AREA)
• Software Systems (AREA)
• Mobile Radio Communication Systems (AREA)
• Transceivers (AREA)
• Small-Scale Networks (AREA)

Abstract

Description

Claims (7)

Priority Applications (1)

Applications Claiming Priority (2)

Related Parent Applications (1)

Publications (1)

Family

ID=33309553

Family Applications (4)

Family Applications Before (1)

Family Applications After (2)

Country Status (6)

Cited By (13)

Families Citing this family (110)

Citations (23)

Family Cites Families (14)

• 2003
  • 2003-04-21 US US10/419,656 patent/US20040255008A1/en not_active Abandoned
• 2004
  • 2004-04-20 KR KR1020057017685A patent/KR100872254B1/en not_active IP Right Cessation
  • 2004-04-20 WO PCT/US2004/012286 patent/WO2004095193A2/en active Search and Examination
  • 2004-04-20 TW TW093110999A patent/TWI351195B/en not_active IP Right Cessation
  • 2004-04-20 EP EP04760075A patent/EP1616240A4/en not_active Withdrawn
  • 2004-04-20 CN CN2004800105915A patent/CN101069173B/en not_active Expired - Fee Related
• 2007
  • 2007-10-29 US US11/926,977 patent/US20080052548A1/en not_active Abandoned
  • 2007-10-29 US US11/927,572 patent/US7752330B2/en not_active Expired - Fee Related
  • 2007-10-29 US US11/926,846 patent/US20080046547A1/en not_active Abandoned

Patent Citations (25)

Also Published As

Similar Documents

Legal Events