Patent Publication Number: US-8116337-B2

Title: Bandwidth requests transmitted according to priority in a centrally managed network

Description:
FIELD OF THE INVENTION 
     This invention relates in general to video, telephony, and data systems over a centrally managed network, and more particularly, to the field of requesting bandwidth for the transmission of video, telephony, and data packets over the network. 
     DESCRIPTION OF THE RELATED ART 
     Network devices, such as cable modems, voice over Internet Protocol (VoIP) gateways, media terminal adapters (MTAs), and set-tops, are typically the interface to the physical telephony and/or video equipment required for packet transport. Today, these network devices provide quality of service (QoS) for video, voice, and data packets generated by phones, computers, or televisions that are connected to the network devices. 
     Due to packet congestion in the access network, QoS is used to create transport guarantees for the video, voice, and data packets dynamically. More specifically, QoS is used in a centrally managed access network to ensure low latency and guaranteed bandwidth for certain packets. Network devices request bandwidth from managing access network devices prior to transmitting packets. Accordingly, the managing access network devices authorize bandwidth depending upon the requested packet priorities (i.e., the requested packet&#39;s QoS). The QoS priorities normally range from 0 through N, where N indicates the most critical packets. Conventionally, however, the network devices, e.g., cable modems, set-top boxes, MTAs, etc., all request bandwidth during a predetermined period resulting in collisions among the bandwidth requests. Additionally, all network devices request at the same time during the predetermined period regardless of priority, so that a priority N request may collide with a priority lower than, or higher than, the N request. Therefore, there is a need for a system and method that allows for bandwidth requests in a centrally managed access network that depends upon a priority of requests in order to avoid request packet collisions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. In the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  illustrates a centrally managed network for transmitting video, voice, and data packets. 
         FIG. 2  is a table illustrating an example of QoS priorities. 
         FIG. 3  is a listing of steps taken by devices within the managed access network for requesting bandwidth in order to transmit packets. 
         FIG. 4  illustrates an example of dedicating bandwidth to specific network devices in a managed access network. 
         FIG. 5  is an example of a managed access network including systems and methods for transmitting requests in accordance with the present invention. 
         FIG. 6  is a listing of steps taken by devices within the managed access network for requesting bandwidth in order to transmit packets in accordance with the present invention. 
         FIG. 7  illustrates example periods within a request time when network devices can request bandwidth depending upon packet priorities. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Preferred embodiments of the invention can be understood in the context of a broadband communications system. Note, however, that the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. All examples given herein, therefore, are intended to be non-limiting and are provided in order to help clarify the description of the invention. 
     The present invention is directed towards systems and methods that allow network devices to request bandwidth based on a packet&#39;s QoS priority. The QoS priority for the packet is mainly determined by the network operator and depends upon many variables, such as number of subscribers and equipment employed in the network. In accordance with the present invention, network devices in the system request bandwidth according to a scheduling map. The scheduling map, which gives specific times within a request period, for requesting bandwidth corresponding with a packet priority, is downloaded to all network devices. Each network device then consults the scheduling map in order to determine the specific time during the request period in which to transmit a request packet. Importantly, since the network devices then transmit requests at different times with the request period, collisions are eliminated or dramatically minimized. Additionally, bandwidth requests for critical priority packets can be grouped together during the different times to ensure that a critical packet request does not collide with a lower packet request. 
       FIG. 1  illustrates a centrally managed access network for transmitting video, voice, and data packets. Managed access network devices  105  are responsible for providing connections between devices that provide for media, signaling, provisioning, and QoS. For example, a call management server (CMS)  110  receives requests for making calls via the managed access network devices  105 . The CMS  110  then initiates and processes signals related to that call. A cable modem terminal system (CMTS)  115  manages sessions over the managed access network  100  utilizing a Data over Cable Service Interface Specification (DOCSIS) protocol. The CMTS  115  is responsible for assuring that all cable modems (CMs) on the network  100  remain synchronized. Typically, an optical node  120  receives the optical signals received from the CMTS  115  and converts the signals to electrical signals. There may be several optical nodes having several CM groups  125 ,  130 ,  135  coupled to an output of one of the optical nodes. An example of one subscriber within a CM group  135  is shown. An RF splitter  145  splits the downstream signals providing signals to a set-top device  150  and a cable modem  155 . The set-top device  150  may be connected to a television or other viewing device for displaying video/audio signals. Additionally, the set-top device  150  may include a reverse transmitter or a cable modem to transmit reverse packets. The cable modem  155  filters signals that are provided to a coupled telephone and/or a computer. Typically, all network devices,  150 ,  155  are two-way capable allowing for interactive transmission of packets between the network device  150 ,  155  and managed access network devices  105 . Furthermore, as mentioned, some of these packets have an associated QoS priority depending upon the application. 
       FIG. 2  is a table illustrating an example of QoS priorities. In this example, a 0 priority indicates a best effort. This may be reserved for Internet browsing. Other lower priorities include 1-3 that may be used for standard or business critical packets. Higher priorities in this example are priorities 4-6, where priority 4 is a controlled load for streaming multimedia and voice, priority 5 for video (e.g., interactive media), and priority 6 for voice calls. Priority 7 may be used for reserved traffic. As mentioned, these QoS priorities may be configurable by the network operator. 
       FIG. 3  is a listing of steps taken by devices within the managed access network  100  for requesting bandwidth in order to transmit packets. In step  305 , the CMTS  115  allocates a predetermined period of time for all CMs within the CM groups  125 ,  130 ,  135  to request bandwidth. During that time, in step  310 , each CM that is ready to transmit packets associated with video, voice, and/or data sends a request indicating some priority associated with the packets. If a request from one CM collides with a request from another CM, in step  315 , the two CMs back off for a short time according to an internal algorithm within the request period to try to avoid further collisions. After the back off time, the two CMs resend the requests. Once the CMTS  115  receives the requests in step  320 , the CMTS  115  allocates bandwidth to the requesting CM according to the specified priority of the packet. For example, if a CM requested bandwidth for packets having a priority of 4, the CMTS allocates bandwidth for this CM before allocating bandwidth to a CM that requested bandwidth for packets having a priority of 0. 
       FIG. 4  illustrates an example of dedicating bandwidth to specific network devices in a managed access network. In order to avoid packet collisions, some operators may choose to give specific network devices, such as CMs, dedicated bandwidths within the frequency spectrum in order to transmit packets at any time. In this case, CM A is assigned exclusivity to transmit within BW 1 . CM A transmits packets to a CMTS  415  via a managed access network and devices  420 . Furthermore, CM B and CM C are assigned exclusivity to transmit packets within BW 2  and BW 3 , respectively. Assigning CMs exclusive bandwidth avoids any collisions with other CMs; however, it requires a great deal of bandwidth that networks seldom have, and the bandwidth is wasted when the CMs do not use it. 
       FIG. 5  is an example of a managed access network including systems and methods for transmitting requests in accordance with the present invention. In order to solve the problems stated above, the present invention continues to have all network devices within all CM groups  125 ,  130 ,  135  transmit requests during a same time period and at a same frequency bandwidth. The network devices, however, transmit requests during specific times within the time period depending upon the priority of the packets. For example, the priorities of packets may range from the following: e-mail packets having a priority of 3 generated by a first CM/MTA  505 , which is connected to a computer; streaming video packets having a priority of 5 generated by a set-top device  510 , which is connected to a television and a camera; voice signals having a priority of 6 generated by a second CM/MTA  515 , which is connected to a telephone; and Internet browsing packets having a priority of 0 generated by a third CM/MTA  520 , which is connected to a computer. In accordance with the present invention, the network devices  505 ,  510 ,  515 ,  520  will transmit requests to a CMTS  525  during the specific time within the request time period according to the generated packet&#39;s QoS. 
       FIG. 6  is a listing of steps taken by devices within the managed access network for requesting bandwidth in order to transmit packets in accordance with the present invention. Initially, in step  605 , the CMTS  525  sends a map message to all network devices in the access network for request scheduling based on the provisioned QoS priority of packets. The network devices store the request schedule in memory for future reference. In step  610 , the CMTS  525  then allocates a period of time, for example, 100 microseconds (μs) every 5 seconds, for the network devices to request bandwidth. During the allocated request time and in accordance with the stored request schedule, in step  615 , the network devices wanting to transmit packets having priorities 4-7 may send request packets during a first period within the allocated request time (i.e., 100 μs), and, in step  620 , network devices wanting to transmit packets having priorities 0-3 may send request packets during a second period within the request time. Generally, since the majority of request packets transmitted are lower in priority, the second period may further be broken down into a third and fourth period. The first period may also be reduced allowing more time to be allocated to any other period to ensure less packet collisions. 
       FIG. 7  illustrates example periods within a request time when network devices can request bandwidth depending upon packet priorities. In accordance with the present invention, CMs transmit requests within a specified bandwidth, such as, for example, at 10 MHz. CMs then transmit the requests to the CMTS  525  via the managed access network  100 . During the specified request time, such as 100 μs every 5 seconds, CMs transmit requests according to the priorities and the schedule map. For example, requests for packet bandwidth having QoS priorities 4-7 may transmit during the first 50 μs  730 . Thereafter, requests for packet bandwidth having QoS priorities 0-3 may transmit during the second 50 μs  735 . As previously mentioned, the time periods can be changed at any time to accommodate changes in the amount of request packets by downloading another map message detailing a new schedule. 
     Accordingly, systems and methods have been provided that allows for the transmission of requests based on the QoS priority of the generated packets. It will be appreciated that further embodiments are envisioned that implement the invention, for example, using all software or adding modes for additional features and services.