Automatic Router Configuration | Solutions and Recommendations

Automatic configuration of the WR is performed using a 4-state machine including a start up state, a learning state, an operational state and a site down state as depicted in Figure 1.

Figure 1: A state machine for dynamic configuration of a wireless router

 

The WR configures the RF/IP topology in the startup state, and refines the topology in the learning state. In the operational state, the wireless router handles a full traffic load, and continues to check if it meets the operational thresholds. Scheduled or unscheduled maintenance leads the WR into site-down state.

1) Start up state: In the starting state, connectivity is first established between the WR and the wire-line routers in the network. The wire-line connectivity is then used to establish connectivity between WR and its WR neighbors. Subsequently, MPLS paths or other suitable virtual circuits or IP tunnels are established among the WR neighbors to facilitate inter-router communication. The WR uses wire-line connectivity to learn from its neighbors the RF topology in the neighborhood, and establish wireless-specific connectivity with its neighbors.

After establishing the wireless connectivity with its WR neighbors, a WR exchanges RF impact information, including some or all of the parameters mentioned earlier. By exchanging this information, and negotiating the various operation parameters, the WR is able to determine or estimate a set of operating parameters that will help maximize radio coverage, minimize interference, and aid in providing a seamless coverage from cell to cell with smooth handovers. If no coordination could be achieved between the wireless routers in a neighborhood, Operation, Administration and Maintenance (OAM) server is contacted for resolving the differences. The OAM server then performs the RF impact analysis and responds with the operational parameters for the new site and the neighboring sites. The OAM server may also re-identify neighbor sites after parameters are agreed to, and store them in the configuration and parameter tables in the routers. The routers transition to the Learning state as shown the figure. Now, a RF system and network has been established by activating the wireless routers.

In the start up state, chores of the WR are: i) identification of the neighbors of the WR and preparation neighbor list, ii) interference impact, coverage, and other parameter analysis, iii) configuration of LSPs with neighbors, and iv) exchange and negotiation of power and handoff parameters with neighbors. In this way, the WR automatically configures itself for operation in the wireless network. Once these operations are completed, it transitions to the learning state.

2) Learning State: In the learning state, the WR continues to analyze, exchange and negotiate parameters, in order to minimize interference in the wireless network and to ensure that all the operational thresholds are met. The WR transitions into this state from the start-up state when RF power is up, and from operation state when either operational parameters change, or the WR neighbors change, or the operational thresholds are not met. In the learning state, parameters are re-negotiated and re-estimated based on the information given during transition from the operational state. Once operational thresholds are met for a specific period of time, the WR transitions to the operational state.

3) Operational State: In the operational state, the WR continues to monitor its operational thresh-olds periodically or otherwise exchanges information with its WR neighbor to ensure maximum efficiency and minimum RF interference within the wireless network. If the operational thresholds are not met, the wireless router transitions from the operational state back to the learning state for detailed analysis and evaluation of the configuration parameters and reconfiguration, as required, so that the operational thresholds can be met.

Also, if any of the neighboring routers change, affecting the topology of the network, such as a neighboring router failure, or a new router is added to the wireless topology, the router transitions from the operational state to the learning state, to reconfigure itself to suit to the new topology. In addition, if any parameters are changed due to any requests from its neighbors, the WR transitions to the learning state, for analysis and evaluation of operation using the new parameters.

4) Site Down state: The wireless router may enter the site down state from the learning state or the operational state if it requires either scheduled or unscheduled maintenance. Upon power up, the router will again transition back to the start up state for reloading and reconfiguration of the operational parameters. In this way, the wireless routers automatically adjust and account for changing conditions in the network to optimize operation of the network.

Mechanisms to Dynamically Configure the Router | Solutions and Recommendations

The proposed WR has been designed for dynamic configuration of its operational parameters. Configuration parameters of a WR are typically related to the site and technology used. Site parameters may be classified as geo-location, network operation, service configuration, and antenna parameters. The technology specific parameters depend upon whether the CDMA or GSM is supported and include technology-specific site parameters, but may be broadly classified into coverage, spectrum, channel, interference, control, and threshold parameters. At a finer level of detail, site Id, number of sectors/beams, sector/beam ID, latitude and longitude, sector/beam location, maximum radius of influence are typical geo parameters. Similarly, network configuration parameters include network interfaces (e.g. Tl, SONET, T3, etc.), site capacity, and network capacity. In the service configuration, we may have the list of various services supported, and the related directory agent (DA) addresses. The antenna parameters listed on a per sector/beam basis include the antenna type, digitized pattern, horizontal/vertical beam widths, max gain, and mechanical and electrical down tilts.

In the technology parameters class, maximum RTD (round trip delay), PER (packet error rate), FER(frame error rate), and percentages of blocked calls, access failures, dropped calls constitute the threshold parameters subclass. The coverage parameters subclass includes environment (e.g. rural or urban), path loss margin, technology specific hardware losses and gains, RF coverage prediction models, and traffic distribution maps. The spectrum parameters subclass consists of channel bandwidth, channel mask, channel number range, and maximum transmit power per channel. The channel parameters include the number of channels in the range, air capacity/bandwidth, minimum channel spacing, frequency use, frequency grouping, and hopping sequences. The interference parameters include interference thresholds, power control thresholds, channelization and sequencing, channel scheduling algorithms, RF interference prediction models, traffic distribution maps, and adjacent channel interference threshold. The control parameters subclass includes access parameters, intra-technology and inter-technology handoff parameters, and timing parameters.

In the following subsection, we present a very high level procedure by which a WR learns its parameters and configures itself in collaboration with its neighbors. The control logic and the operations performed in each high level state could be quite complex with several states for error paths and exceptions. For example, application of RF or IP discovery protocols in the startup state involves considerable information exchange between a WR and its neighbors.

High QOS with Traffic Control for Effective Bandwidth Management | Solutions and Recommendations

Overloading of a wireless network could occur because of the heavy data traffic. Traffic flow control for effective management of transmission resources, particularly the bandwidth, facilitates high quality of service (QOS). For example, by shaping (that is, spacing) the data traffic which usually comes in bursts unlike the voice traffic, the network bandwidth could be utilized more effectively. On the other hand, overloading of the wireless network even for short durations of time could result in degradation of QOS due to increased bit error rates.

Figure 1 depicts the different feedback controls used in our system for traffic flow adjustment for effective data transmission. Signal power of the mobile device or any other direct indicator of power for the RF link constitutes the inner power control just as in the traditional wireless systems. This feedback is provided every 1 -2 milliseconds. Similarly, outer power comprises a link error rate and/or interference indicator for the wireless link and may account for soft handoff power. This feedback may be provided every 50-100 milliseconds. The inner and outer power control loops conjointly provide feedback based on the signal strength of the RF link. The packet level control is provided every several hundred milliseconds by the queuing system in the WR based on the congestion status of the queues. Finally, our repertoire of traffic control mechanisms included the well known and well studied TCP flow control, which is provided through the acknowledgment messages between the two end points of the TCP flow. Based on the acknowledgment messages received, the source (WR) adjusts its transmission rate. Thus, with this mechanism, traffic flow is controlled by the congestion and/or interference state of the wireless links.

Figure 1: Feedback mechanism for traffic flow control

 

In our WR, there is also a provision for the traditional end-to-end rate control with a queue mechanism to shape up bursty traffic from a source into a smooth traffic flow of radio frames into the sink (mobile). The ACKs from the sink are also similarly queued up, and used as feedback for the source so that it can control its egress traffic flow.

An innovative flow control mechanism in the present work is Gang (or Group) flow control which seeks to shape the TCP flows from various sectors of the wireless network simultaneously, shown as Figure 2 with N acknowledge shapers corresponding to N sectors of the WR. Each shaper accepts the packets from wireless network and stores the packets in the acknowledge queues inside the WR. The acknowledge shaper can transmit acknowledge message over time to change the traffic flow for the sector based on the flow's power indicator of the RF link from wireless network.

Figure 2: Gang flow control for sectors of a wireless

 

Figure 2 illustrates two kinds of shaped acknowledge messages. In the first type shown for flows 1 and 2, the acknowledge messages are arranged in small groups and the groups are dispatched periodically. In the second type depicted for Flow N, on the other hand, the ACKS are evenly distributed overtime and transmitted. The difference of these two arrangements is that they have different transmit time. The first type of ACK shaping will affect the offsetting bursts for the traffic flow whereas the second type will affect the steady flow rate for the traffic flow.

The flows with unused bandwidth or lack of bandwidth will be identified for each TCP group for the interval related to retransmission time out for the TCP flow. The fair share of each TCP flow within the group will be calculated and used in adjusting the speed of acknowledge messages for the flows inside the gang. The fair share of each TCP flow may be used together with the RTT and arrival time for each traffic flow.

Call Processing and Soft Handoff Mechanism | Solutions and Recommendations

Figure 1 depicts interactions among various network elements for ingress data (i.e. data flowing from the mobile device to the edge router. Figure 2 depicts the interactions for the egress data flowing in the reverse direction. These figures are OO (object-oriented) style sequence diagrams for call flow in an UML (Universal Modeling Language) like notation.

Figure 1: Data transfer from the mobile device to an edge router

 

Figure 2: Soft hand off and data transfer from an edge router to the mobile

 

In both the scenarios described here, the first step is designation of one of the routers accessible to the mobile device as the primary router. In case of mobile originated calls, the mobile informs the WR from whom the strongest signal is received to take the responsibility as prime WR. On the other hand, in case of mobile terminated calls, the edge router determines the prime router based on the mobile location after locating and successfully paging the mobile. Once the primary router is determined, it initiates the process for setting MPLS tunnels between itself and the edge router as well as the secondary routers. The key innovation here is to employ these MPLS tunnels to emulate the BS-BSC and BSC-MSC (mobile switching center) A3/A7 interfaces in the legacy wireless systems. Distribution of call flow control this way among various routers this way results in enormous cost savings for the customers due to effective utilization network links by reduction of the call control and data paths. Figures 1 and 2 depict the call flows after creation of MPLS tunnels.

In case of ingress data, the radio frames transmitted by the device are received by all active routers including a primary router and a number of secondary routers as shown in Figure 1. The secondary routers simply forward the radio frames to the primary router. The SDU of the primary WR selects the best one among all such frames including the one directly received, inserts that into an IP packet, and transmits it to a back-haul network via an edge router for onward transmission to the other party.

The flow in case of egress data is naturally in the opposite direction as shown in Figure 2. The core network hands over the IP packets to an edge router for onward transmission to the primary router through a pre-established or dynamic MPLS path. The primary WR segments the packets into radio frames and multicasts them to all the secondary WRs in the active set via dynamically configured Label Switch Paths (LSPs). The primary and secondary WRs then transmit each one of these received radio frames after different amounts of delay offset to the mobile device so that the replicas of individual frames from different WRs arrive simultaneously at the destination. These synchronous radio frames received from different WRs are analyzed by the mobile device to not only obtain the best (correct) radio frame, but also assess the power levels of the frames. As the mobile device moves away from the primary WR, the power level of the radio frames from the mobile at the primary as well as that of the frames from the primary at the mobile drop. When the power level drops below a pre-configured threshold, the mobile device sends a control message to the primary WR indicating the power level of the prospective primary. The new primary WR could be one of the previous secondary wireless routers in an active set for the call. To achieve micro mobility, the current primary WR would signal the new primary an indication of the handover of its responsibility as primary WR. It would also supply to the latter the list of active WRs in the same control message. After receiving this message, the new primary WR receiving the strongest signals first confirms to the current primary that it is ready to take control of the traffic distribution, and then establishes multicast MPLS paths (LSPs) for the secondary routers in the active list. The LSPs provide synchronized framing for distribution and selection between neighbors of wireless traffic and fast rerouting for soft handoff using RSVP.