Abstract:
A method and apparatus for routing packet data in a communications system. The method includes receiving a first path packet at first node, the first path packet having a content, creating two packets having the content, sending the two packets via different paths to a second node, and creating an estimated packet including an estimate of the content in response to the two packets received at the second node. In addition, a method for providing soft handoff in a cellular communication system is provided, the method including receiving a first path packet at a first node, the first path packet having a content within the first node, creating two packets having the content, sending the two packets to a transmitter, transmitting the two packets via two different radio channels to a second node, and creating an estimated packet including an estimate of the content in response to the two packets received at the second node.

Description:
RELATED APPLICATIONS 
     The following applications are related to this application and are filed on the date herewith. The disclosure of each of these related applications is incorporated by reference: Ser. No. 09/315,277, filed May 20, 1999 titled “METHOD FOR CHANGING COMMUNICATION IN A COMMUNICATION SYSTEM, AND COMMUNICATION SYSTEM THEREFOR”; Ser. No. 09/315,696, filed May 20, 1992, now U.S. Pat. No. 6,192,037 titled “METHOD FOR ESTABLISHING COMMUNICATION IN A PACKET NETWORK”; Ser. No. 09/314,908, filed May 20, 1999, titled “METHOD FOR RETRANSMITTING A DATA PACKET IN A PACKET NETWORK”; Ser. No. 09/315,314, filed May 20, 1999, titled “COMMUNICATION NETWORK METHOD AND APPARATUS”; Ser. No. 09/315,467, filed May 20, 1999, titled “METHOD AND SYSTEM FOR PROCESSING INTELLIGENT NETWORK COMMANDS IN A COMMUNICATIONS NETWORK”; Ser. No. 09/315,653, filed May 20, 1999, titled “METHOD AND SYSTEM FOR NETWORK SERVICE NEGOTIATION IN A TELECOMMUNICATIONS SYSTEM”; Ser. No. 09/315,309, filed May 20, 1999, titled “SESSION BASED BILLING IN A COMMUNICATION SYSTEM”; Ser. No. 09/315,466, filed May 20, 1999, titled “METHOD AND SYSTEM FOR INTRODUCING NEW SERVICES INTO A NETWORK”. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a communications system, and more particularly, to a method and apparatus for routing data within the communications system. Still more particularly, the present invention relates to a method and apparatus for increasing the quality of a network transmission between a first node a second node, and a method for providing soft handoff in a cellular communications system. 
     BACKGROUND OF THE INVENTION 
     In a conventional telecommunications switching network, a communications path must be established in a source node and a destination node before data, such as facsimile, email, or voice, can be distributed along the established path. A propagation delay occurs across the network when setting up and releasing a communication path. Conventional telecommunications switching systems, upon deriving a destination of a telephone call, must send a message to a remote database system to request routing information for a particular call. Remote database systems provide a menu of routing information, and routing information is selected from the database system according to the request from a telecommunications switching system. 
     Code division multiple access (CDMA) systems must support the transport of digitally encoded information that is in packet form. In addition, CDMA systems must support multiple duplicated streams of this information, known as soft handoff, and carry this information in an efficient manner over transport links within the system. Large CDMA systems may require different networking technology. Implementation of an Internet Protocol (IP) based network can solve transparency issues with the network by providing the inter networking function above the physical and transport network layers. The cost of network equipment in a CDMA system is a problem because of the large number of network paths required because of the use of soft handoff. Another problem with the large number of network paths in a CDMA system is the complexity of manipulation and management of these paths in a connection oriented implementation. IP allows a connection less or routed architecture that greatly simplifies network implementation. Unlike other technologies such as Asynchronous Transfer Mode (ATM), the use of differentiated services to assign and/or control quality of service (QoS) enables this to be done in a connectionless manner in the core network where bandwidth is prevalent. 
     In addition, a routed network enables a peer-to-peer network element relationship rather than the classical hierarchical network. A peer-to-peer network allows for entity relationships such as client/server which offers improved and flexible possibilities for scalability and network robustness. 
     It is, therefore, desirable to have an improved method and apparatus for routing packet data in a communications system, wherein the quality of a network transmission between a first node and a second node is increased. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objects, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 depicts a block diagram of a communications system in which the present invention may be implemented; 
     FIG. 2 depicts a block diagram of data structures according to the present invention used to transfer data within a communications system; 
     FIG. 3 depicts a block diagram of an embodiment of the present invention; 
     FIG. 4 depicts a block diagram of an alternate embodiment of the present invention; and 
     FIG. 5 depicts a more detailed block diagram of an embodiment of the present invention as it relates to a CDMA system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference now to the figures, and in particular with reference to FIG. 1, a communications system  100  is depicted in which the present invention may be implemented. Communications system  100  includes an interconnect network, which may be a packet system but which in the preferred embodiment is an IP network which processes data streams from various sources, such as voice, data, image, and video. IP network  102  receives and sends data to and from cellular regions  104  and  106 . Cellular region  104  includes base termination sites (BTSs)  108 - 112 , which send and receive radio signals to and from mobile telephones and packetize the communications content of the radio signals into electronic data transported within data packet units. The packets are sent to IP network  102  over the span lines connecting BTSs  108 - 112 . These span lines may be T 1  or E 1  lines connecting the BTS to IP network  102 . Similarly, cellular region  106  contains BTSs  114 - 118 , which also receive radio signals, packetize these signals into data packet units, and send the data packet units to IP network  102  over the span lines connecting BTSs  114 - 118  to IP network  102 . 
     Data can be sent to mobile telephone units, such as mobile unit  120 , from IP network  102  through transmissions from BTSs located in each of the cellular regions. A mobile unit  120  traveling within cellular region  106  transmits radio signals for a call that may be received by more than one BTS, such as BTSs  116  and  118 . Each BTS receiving a radio signal from mobile unit  120  will transmit data to IP network  102 , via the span lines. At some point, only one of the two BTSs will receive radio signals from the mobile unit  120  because the mobile unit  120  will have traveled out of the range of that BTS. Similarly, a mobile unit may receive a radio signal from more than one BTS depending on the location of mobile unit  120 . This receiving of radio signals at multiple BTSs for a signal call is associated with soft handoff (SHO). 
     With reference now to FIG. 2, a block diagram of data structures used to transfer data in communications system  100  in FIG. 1 is depicted according to the present invention. Packet  200  is an electronic data packet in the form of a code division multiple access (CDMA) packet received within one of the BTSs shown in FIG. 1, such as BTS  118 . Packet  200  includes data streams associated with CDMA. When received at BTS  118 , packet  200  is transformed into a packet data unit (PDU)  202 . PDU  202  is sent to IP network  102 . PDU  202  is an example of the data structure used within IP network  102  to carry data from source nodes to destination nodes. PDU  202  comprises a content which includes a header portion  204  and, a payload portion  206 . Header portion  204  includes information used to route the PDU  202  along with other overhead information. Data is placed within payload portion  206 . 
     With reference now to FIG. 3, a communications system  300  is depicted in which the present invention may be implemented. Communications system  300  includes an IP network  302  which processes data streams from various sources, such as voice, data, image, and video. IP network  302  receives and sends data to and from cellular regions  304  and  306 . IP network  302  includes access node/router  303 , which sends and receives data streams to and from base termination sites  308  and  318 . Cellular region  304  includes base termination site (BTS)  308 , which sends and receives radio signals to and from mobile telephones and packetizes the communications content of the radio signals into electronic data transported within data packet units. The packets are sent to IP network  302  over the span lines connecting BTSs  308  and  318 . Alternatively, the packets may be sent over fiber, microwave, etc. Similarly, cellular region  306  contains BTS  318 , which also receives radio signals, packetizes signals into data packet unit, and sends the data packet units to IP network  302  over the span lines connecting BTS  318  to IP network  302 . With regard to downlink traffic, access node/router  303  receives an incoming data stream from a node within IP network  302 , the data stream having a content including a header portion and a payload portion. Within node  303 , two packets are created having the content, one of the packets being sent to BTS  308  and the other of the packets being sent to BTS  318 . In the preferred embodiment, the two packets are transmitted via two different logical channels over a shared broadband spectrum to a second node, which, as shown in FIG. 3, is mobile unit  320 . At mobile unit  320 , an estimated packet is created having an estimate of the content in response to the two packets received from BTS  308  and BTS  318 . In a CDMA system, the creation of an estimated packet includes aligning the packets received from BTS  308  and BTS  318 , and summing the packets received from BTS  308  and BTS  318 . In an alternate embodiment, a quality of service (QoS) function may be added, the QoS function being described in more detail below. 
     Referring to FIG. 4, a block diagram of an alternate embodiment of the present invention is shown at  400 , wherein access node/router  404  receives an incoming data stream from selection/distribution node  402 , the data stream having a content. Within node  404 , the data packet is replicated, whereby two packets are created having the content, one of the packets being sent to transmitter  406  and the other of the packets being sent to transmitter  408 . Subsequently, the replicated packet is sent or transmitted to node  410 . At node  410 , an estimated packet is created having an estimate of the content in response to the two packets received from transmitters  406  and  408 . In an alternate embodiment, a quality of service function  412  may be added, the quality of service function  412  providing a mechanism to weigh the cost of resources and the system availability of resources. This facilitates the decision to maintain or remove one or more of the multiple paths being used in the network connection between nodes  404  and  410 . For example, a decision can be made about the quality of each of the multiple paths, thereby enabling one of the paths to be selected over another one of the paths or even enabling one of the paths to be torn down. 
     With reference now to FIG. 5, a block diagram of an embodiment of the present invention as it relates to a CDMA system is shown wherein soft handoff with paths including BTS-A and BTS-B is shown. As seen in FIG. 5, in the preferred embodiment, each physical bearer end point will be individually IP addressable. For example, in BTS-A  504 , channel  1  has the IP address IP:A 1 , channel  2  has the IP address IP:A 2 , etc. In BTS-B  506 , channel  1  has the IP address IP:B 1 , channel  2  has the IP address IP:B 2 , etc. Referring to the selector  508 , the address for channel (N) is IP:S(N). Referring to the vocoder  510 , the IP address of vocoder (N) is IP:V(N). Traffic is routed among the physical elements via standard IP routing and, in the preferred embodiment, by a connectionless IP protocol such as UDP for transport of bearer traffic. For example, uplink traffic (e.g., BTS to vocoder) is routed as follows: 
     channel element BTS-A- 1  to selector channel  1  (source IP address IP:A 1 , destination IP address IP:S 1 ) 
     channel element BTS-B- 1  to selector channel  1  (source IP address IP:B 1 , destination IP address IP:S 1 ) 
     selector channel  1  to vocoder  1  (source IP address IP:S 1 , destination IP address IP:V 1 ) 
     The reverse is generally true for the downlink except that in the preferred embodiment, IP multicast such as Internet Group Management Protocol (IGMP) is used to allow the distribution function to provide a copy of an incoming sample stream to each of the multiple BTSs involved in soft handoff. In this case, channel element BTS-A- 1  (IP:A 1 ) and channel element BTS-B- 1  (IP:B 1 ) belong to a common multicast group that the distribution function (selector channel  1 ) sends to. As the call configuration changes, soft handoff legs add and drop, and BTS channel elements enter and leave the multicast group, respectively. 
     Referring back to FIG. 5, the following description pertains to tracing the voice path through the system  500  for the downlink. Voice will flow from the PSTN (not shown) to vocoder  510 . An alternative flow may be from the internet or other multimedia device through unit  518  and then to selection/distribution unit  508 . Voice can be carried by that path as well (e.g., voice over IP). The voice stream thereafter gets fed over to the selection/distribution unit  508 . More particularly, the voice stream flows out the IP path coupling vocoder  510  and IP routing/switching unit  514  and thereafter gets routed to selection distribution unit  508 . In other words, the voice stream is essentially an IP datagram that is routed to a specific selection/distribution unit that is handling this particular call. The data packet is thereafter replicated via IGMP in one of the access node/routers  512 ,  516  or IP routing/switching unit  514 . 
     IP routing/switching unit  514  and access nodes  512 ,  516  essentially provide media adaptation and IP datagram routing. IP routing/switching unit  514  in essence just takes in an IP datagram and routes it. Access nodes or routers  512 ,  516  typically bring in a plurality of fairly low speed links such as T 1  and multiplexes those at that point. 
     Subsequently, the replicated packet is sent via different paths to BTS-A  504  and BTS-B  506 . Thereafter, each of the BTSs  504  and  506  will take the payload out of the packet and convert the payload into a form that is suitable for wireless transmission and thereafter transmit the packet in a synchronized fashion or a timed aligned fashion to the mobile subscriber unit  502 . It should be noted that the same flow as described above for a voice path could occur for data such as data off of the internet or a multi-media service as shown at alternative data path unit  518 . 
     It is contemplated that the mobile subscriber  502  itself be the IP capable end point. In that instance, mobile subscriber  502  is then the multicast group and the BTSs  504  and  506  then act as multicast routing proxies as members of the IP network. As a mobile moves (hands off) from one BTS to another, the multicast routing tree is updated as other BTSs get involved and/or leave the call. 
     IP multicast via a protocol such as internet group management protocol (IGMP) can also be used to distribute control messages, such as mobile paging requests, from a central control function such as controller  520  to the BTSs  504  and  506 . For example, each paging area may correspond to a unique multicast group. BTSs that belong to a given paging area would join the multicast group associated with that area. Each BTS may be a member of multiple paging areas and thus would belong to multiple multicast groups. To deliver a page, the controller  520  would send a page control message to the multicast group associated with the paging area to be paged. Only the BTSs that need to actually page the subscriber will receive the page control message. Simple broadcast can also be used for this function or when the page is effectively a “page all” request. The aforementioned also may be applied to realize other features such as short message service (SMS). 
     The foregoing description of a preferred embodiment of the invention has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application, and to enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.