Adaptive digital access protocol: a MAC protocol for multiservice broadband access networks
TL;DR: The authors describe a protocol that can adapt to the changing demands of a mix of synchronous transfer mode (STM) and asynchronousTransfer mode (ATM) applications and efficiently allocate bandwidth to a variety of bursty traffic sources and its performance with respect to throughput, latency, and bandwidth efficiency is examined.
Abstract: The authors describe a protocol that can adapt to the changing demands of a mix of synchronous transfer mode (STM) and asynchronous transfer mode (ATM) applications and efficiently allocate bandwidth to a variety of bursty traffic sources. In the case of a hybrid fiber-coaxial (HFC) network, the protocol resides in customer premises equipment (CPE) and a common head-end/central-office (HE/CO) controller. A medium-access control (MAC) processor provides for dividing the time domain for a given digital bitstream into successive frames, each with multiple STM and ATM time slots. Within the STM region of a frame, variable-length time slots are allocated to calls (e.g., telephony, video telephony) requiring different amounts of bandwidth. In the upstream channels, a contention access signaling time slot is also provided in the STM region for call control and setup requests. Within the ATM region, fixed-length time slots accommodate one individual ATM cell. These ATM time slots may be reserved for a user for either the duration of a call or a burst of successive ATM cells, or shared via a contention process. At least one contention time slot is available for signaling messages related to ATM call control and setup requests. The MAC-layer protocol, its relation to circuit- and ATM-amenable applications, and its performance with respect to throughput, latency, and bandwidth efficiency for several service scenarios are examined.
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Patent•
09 Jan 1997
TL;DR: In this article, a method and device are provided for controlling access to data, where portions of the data are protected and rules concerning access rights to data are determined, and a method is also provided for distributing data for subsequent controlled use of those data.
Abstract: A method and device are provided for controlling access to data. Portions of the data are protected and rules concerning access rights to the data are determined. Access to the protected portions of the data is prevented, other than in a non-useable form; and users are provided access to the data only in accordance with the rules as enforced by a mechanism protected by tamper detection. A method is also provided for distributing data for subsequent controlled use of those data. The method includes protecting portions of the data; preventing access to the protected portions of the data other than in a non-useable form; determining rules concerning access rights to the data; protecting the rules; and providing a package including: the protected portions of the data and the protected rules. A user is provided controlled access to the distributed data only in accordance with the rules as enforced by a mechanism protected by tamper protection. A device is provided for controlling access to data having protected data portions and rules concerning access rights to the data. The device includes means for storing the rules; and means for accessing the protected data portions only in accordance with the rules, whereby user access to the protected data portions is permitted only if the rules indicate that the user is allowed to access the portions of the data.
1,471 citations
Patent•
22 May 1998TL;DR: In this paper, a method for conflict resolution among remote hosts in a wireless network where remotes make bandwidth requests to the base station via uplink frames partitioned into one or more reservation minislots, a collision occurs where two or more remotes have transmitted a request in the same minislot.
Abstract: In a method for conflict resolution among remote hosts in a wireless network where remotes make bandwidth requests to the base station via uplink frames partitioned into one or more reservation minislots, a collision occurs where two or more remotes have transmitted a request in the same minislot. Each remote is characterized by a stack level, and only remotes with a stack level equal to 0 are permitted to transmit access request packets. Newly active remotes are allowed to join in with those remotes already having stack level 0 during any particular conflict resolution period by setting their stack levels to 0 and entering the request state. If the stack level of a remote is 0, the remote randomly picks a minislot for transmission of an access request. If the outcome is SUCCESS, and the queue at the remote is empty, the remote transmits the current packet after receiving a transmit permit and exits the request state. If the queue is not empty, then, after receiving a permit, the current packet is transmitted with a piggybacked reservation request for transmission of the next packet in the queue, continuing until the queue is empty. If the outcome of the reservation request was not SUCCESS, the remote participates in a random draw to determine whether to increment its stack level by 1 or leave it at 0. If the stack level of any remote is not 0, then in one embodiment if the outcome of the previous reservation request was COLLIDED, the remote increments its stack level by 1, otherwise decrementing it by 1. In an alternate embodiment, if the outcome of all the reservation requests during the previous cycle was COLLIDED for greater than or equal to some threshold, the remote increments its stack level by 1, otherwise decrementing it by 1. The number of reservation minislots available in any particular uplink frame may be dynamically changed based on the percentage of idle minislots and the total uplink queue length.
223 citations
Patent•
09 Feb 2001
TL;DR: In this paper, a number of features for enhancing the performance of a cable transmission system in which data is transmitted between a cable modem termination system at a head end and a plurality of cable modems located different distances from the head end are discussed.
Abstract: A number of features for enhancing the performance of a cable transmission system in which data is transmitted between a cable modem termination system at a headend and a plurality of cable modems located different distances from the headend. The power transmission level, slot timing, and equalization of the cable modems are set by a ranging process. Data is transmitted by the modems in fragmented form. Various measures are taken to make transmission from the cable modems robust. The upstream data transmission is controlled to permit multiple access from the cable modems.
217 citations
Patent•
30 Apr 2004
TL;DR: In this paper, a client sends a request to a WGPS to access a service provided by a site in the walled garden, which traps the message from the client and looks up the site in a table to determine the access control list (ACL) for the site.
Abstract: A user's set top box (STB), or other client, executes a shell and has an application program interface (API) by which certain features of the client can be controlled. The client is in communication with a walled garden proxy server (WGPS), which controls access to a walled garden. The walled garden contains links to one or more servers providing network-based services. The client sends a request to the WGPS to access a service provided by a site in the garden. To provide the service, the site sends the client a message containing code calling a function in the API. The WGPS traps the message from the site and looks up the site in a table to determine the access control list (ACL) for the site. The ACL is a bit-map that specifies which functions of the client's API can be invoked by code from the site. The WGPS includes the ACL in the header of the hypertext transport protocol (HTTP) message to the client. The shell receives the message and extracts the ACL. The shell uses the ACL to determine whether the code has permission to execute any called functions in the API. If the code lacks permission, the shell stops execution and sends a message to the site indicating that the site lacks permission. Otherwise, the shell allows the code to call the function.
186 citations
Patent•
29 Nov 2002TL;DR: In this paper, the synchronization frame and the cell search preamble are used to estimate time and frequency synchronization in an OFDMA-based cellular system, and a cyclic prefix is used to track the frequency, the synchronization preambles are used for symbol synchronization, and the search cell is used for searching cells.
Abstract: In an OFDMA-based cellular system, a frame of a downlink signal includes a common slot and traffic slots. The common slot includes a synchronization preamble and a cell search preamble. The synchronization preamble has a structure for synchronizing time and frequency, and the cell search preamble has a cell search structure. The traffic slot includes pilot symbols provided on the time and frequency axes. A cyclic prefix is used to estimate initial symbol synchronization, and the initial symbol synchronization and the synchronization preamble are used to synchronize the frame. The synchronization frame and the cell search preamble are used to estimate time and frequency synchronization. The cell search preamble is used to search cells. When the initial synchronization is performed, the cyclic prefix is used to track the frequency, the synchronization preamble is used to track symbol synchronization, and the cell search preamble is used to track fine frequency synchronization.
153 citations
References
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01 Apr 1975
TL;DR: Roberts investigates methods of increasing the effective channel capacity of such a channel and proposes to consider the channel to be slotted into segments of time whose duration is equal to the packet transmission time, and to require the devices to begin a packet transmission at the beginning of a time slot.
Abstract: This paper was originally distributed informally as ARPA Satellite System Note 8 on June 26, 1972. The paper is an important one and since its initial limited distribution, the paper has been frequently referenced in the open literature, but the paper itself has been unavailable in the open literature. Publication here is meant to correct the previous gap in the literature.As the paper was originally distributed only to other researchers intimately familiar with the area covered by the paper, the paper makes few concessions to the reader along the lines of introductory or tutorial material. Therefore, a bit of background material follows.ALOHA packet systems were originally described by Abramson ("The ALOHA System--Another Alternative for Computer Communication," Proceedings of the AFIPS Fall Joint Computer Conference, Vol. 37, 1970, pp. 281--285). In an ALOHA a single broadcast channel is shared by a number of communicating devices. In the version originally described by Abramson, every device transmits its packets independent of any other device or any specific time. That is, the device transmits the whole packet at a random point in time; the device then times out for receiving an acknowledgment. If an acknowledgment is not received, it is assumed that a collision occured with a packet transmitted by some other device and the packet is retransmitted after a random additional waiting time (to avoid repeated collisions). Under a certain set of assumptions, Abramson showed that the effective capacity of such a channel is 1/(2e).Roberts in the present paper investigates methods of increasing the effective channel capacity of such a channel. One method he proposes to gain in capacity is to consider the channel to be slotted into segments of time whose duration is equal to the packet transmission time, and to require the devices to begin a packet transmission at the beginning of a time slot. Another method Roberts proposes to gain in capacity is to take advantage of the fact that even though packets from two devices collide in the channel (i.e., they are transmitted so they pass through the channel at overlapping times), it may be possible for the receiver(s) to "capture" the signal of one of the transmitters, and thus correctly receive one of the conflicting packets, if one of the transmitters has a sufficiently greater signal than the other. Roberts considers the cases of both satellite and ground radio channels.
1,480 citations
TL;DR: The performance of the R-ALOHA protocol for multiple access is studied and numerical results from both analysis and simulation are presented to illustrate the accuracy of the analytic models as well as performance characteristics of the rhoHA protocol.
Abstract: In packet broadcast networks, users are interconnected via a broadcast channel. The key problem is multiple access of the shared broadcast channel. The performance of the R-ALOHA protocol for multiple access is studied in this paper. Two user models with Poisson message arrivals are analyzed; each message consists of a group of packets with a general probability distribution for group size. In the first model, each user handles one message at a time. In the second model, each user has infinite buffering capacity for queueing. Analytic models are developed for characterizing message delay and channel utilization. Bounds on channel throughput are established for two slightly different protocols. Numerical results from both analysis and simulation are presented to illustrate the accuracy of the analytic models as well as performance characteristics of the R-ALOHA protocol.
131 citations
TL;DR: An adaptive MAC-layer protocol that supports multiservice (STM and ATM) applications in the context of subscriber access to tree and branch networks, and its performance with respect to signaling throughput and latency, and bandwidth efficiency for several service scenarios is described.
Abstract: Described here is an adaptive MAC-layer protocol that supports multiservice (STM and ATM) applications in the context of subscriber access to tree and branch (e.g., fiber-coaxial cable) networks. The protocol adapts to changing demands for a mix of circuit and cell mode applications, and efficiently allocates upstream and downstream bandwidth to a variety of bursty and isochronous traffic sources. In the case of a hybrid fiber-coaxial (HFC) network the protocol resides in customer premises equipment and a common head-end controller. A medium-access control (MAC) processor provides for dividing the time domain for a given digital bitstream into successive frames, each with multiple STM and ATM time slots. Within the STM region of a frame, variable length time slots are allocated to calls (e.g., telephony, video telephony) requiring different amounts of bandwidth. A contention access signaling channel is also provided in this region for call control and set-up requests. Within the ATM region fixed-length time slots accommodate one individual ATM cell. These ATM time slots may be reserved for a user for the duration of a call or burst of successive ATM cells, or shared via a contention process. At least one contention time slot is available for signaling messages related to ATM call control and set-up requests. Further, the fixed-length ATM time slots may be reserved by a user for the duration of a call, or shared through a contention process. This paper describes the MAC-layer protocol, its relation to circuit- and ATM- amenable applications, and its performance with respect to signaling throughput and latency, and bandwidth efficiency for several service scenarios.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
10 citations
TL;DR: The IEEE 802.14.1 standard for hybrid fiber-coax cable-TV systems is described in this paper, where the technical challenges, the standard development process and an update on its status as of September 1995 are discussed.
Abstract: This paper outlines the development of the Institute of Electrical and Electronics Engineers (IEEE) Project 802.14. This working group is chartered to develop standards for the medium access and physical layers for hybrid fiber-coax cable-TV systems that will deliver integrated multiple services (data, audio and video) to the home. Also discussed are the technical challenges, the standard development process and an update on its status as of September 1995.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
6 citations
TL;DR: This paper summarizes the ATM over HFC definition work taking place in the ATM Forum's Residential Broadband Working Group and the standards progress in the IEEE P802.14 Cable TV Media Access Control and Physical Protocol Working Group.
Abstract: Cable TV companies and regional Bell operating companies, e.g. PacBell, are preparing for the future by installing or rebuilding existing all-coaxial cable plants into hybrid-fiber coaxial plants and by offering a wide range of interactive services which they feel will be most attractive to their subscriber base. These new-to-cable services span a wide range of performance attributes, each placing its own demands on the capabilities of the broadband bearer service system. These services include, but are not limited to: video-on-demand, digital video, video telephony, voice telephony, and a suite of interactive digital data services ranging from traditional Internet and information service access (e.g., Compuserve and Prodigy) to multi-player gaming. The future broadband infrastructure challenge can be met by developing a novel family of integrated bearer service products which communicate using asynchronous transfer mode protocols over the cable TV network. This paper summarizes the ATM over HFC definition work taking place in the ATM Forum's Residential Broadband Working Group and the standards progress in the IEEE P802.14 Cable TV Media Access Control and Physical Protocol Working Group. Finally, an example of bridging Ethernet packets over ATM over HFC is discussed. This paper focuses on the aspects of ATM and the MAC layer and does not detail the rf or physical environment.
4 citations