End-to-end delay management for distributed communications networks

Notice: More than one reissue application has been filed for the reissue of U.S. Pat. No. 8,743,718. The reissue applications are reissue application Ser. No. 15/173,203 filed Jun. 3, 2016; continuation reissue application Ser. No. 16/525,277 and this continuation reissue application Ser. No. 17/740,184. All reissue applications are reissues of the same issued U.S. Pat. No. 8,743,718 (application Ser. No. 13/165,294 filed Jun. 21, 2011).The present application is related to commonly assigned and co-pending U.S. patent application Ser. No. 11/839,086 (hereafter “the '086 Application”) entitled “DELAY MANAGEMENT FOR DISTRIBUTED COMMUNICATIONS NETWORKS”, filed on Aug. 15, 2007 (currently pending). The present application is also related to commonly assigned and co-pending U.S. patent application Ser. No. 13/019,571 (hereafter “the '571 Application”) entitled “DELAY MANAGEMENT FOR DISTRIBUTED COMMUNICATIONS NETWORKS”, filed on Feb. 2, 2011. The '086 Application and the '571 Application are incorporated herein by reference in their entirety.

Distributed antenna systems are widely used to seamlessly extend coverage for wireless communication signals to locations that are not adequately served by conventional base stations or to distribute capacity from centralized radio suites. These systems typically include a host unit and a plurality of remote units. The host unit is typically coupled between a base station or radio suite and the plurality of remote units in one of many possible network configurations, such as hub and spoke, daisy-chain, or branch-and-tree. Each of a plurality of remote units includes one or more antennas that send and receive wireless signals on behalf of the base station or radio suites.

One common issue in distributed antenna systems is adjusting for the different delay associated with each of the remote units. Each remote unit is typically located at a different distance from the host unit. To allow the various antennas to be synchronized, a delay value is typically set at each remote unit. Unfortunately, conventional techniques used to establish the delay for the various remote units have added significant complexity and/or cost to the distributed antenna system. For example, some common network synchronization techniques involve the use of various locating technologies, such as global positioning systems (GPS), that add further complexities and cost to operating these distributed antenna systems reliably and efficiently.

For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for improvements in delay management for distributed communications networks.

A method for calculating delay in a distributed antenna system includes sending a ping initiation message from a remote node to a host node in a distributed antenna system. The ping initiation message uniquely identifies a first communication port of the remote node to the host node with a unique identification. The method also includes receiving a ping reply message at the remote node. The ping reply message corresponds to the ping initiation message and also uniquely identifies the first communication port of the remote node with the unique identification. The method also includes determining, at the remote node, whether the ping reply message corresponds to the first communication port of the remote node based on the unique identification. The method also includes, when the ping reply message corresponds to the first communication port of the remote node, calculating the round-trip time delay between sending the ping initiation message and receiving the ping reply message at the remote node.

The following detailed description relates to delay management for distributed communications networks, such as a distributed antenna system. The delay management discussed here enables a network manager to establish a desired delay at a plurality of remote nodes in a point-to-multipoint or multipoint-to-multipoint communications network with a suitable high degree of repeatability and control. The desired delay can be for each of the remote nodes collectively or for each individual remote node. Advantageously, the communications network discussed here uses an end-to-end approach to determine a signal path delay from a host node to each remote node in the system. This is accomplished at each remote node by discovering a signal path delay (such as the travel time) over the link between the remote node and a host node. The signal path delay between each remote node and a host node accounts for individual processing delays of the remote nodes.

Once the signal path delays for each of the remote nodes are determined, the desired delay at each remote node can be definitively established by accounting for the signal path delay back to the host node and any known internal processing delays. In this manner, every remote node in the system is constantly aware of its distance (in signal time) from the host node. This allows each remote node to independently adjust the delay of its transmissions to maintain a selected delay in the system at each of the nodes. While much of this description describes an embodiment having a single host node, other embodiments include multiple host nodes connected to various remote nodes. In addition, signal path delays may be calculated from the remote node to a plurality of different host nodes.

Furthermore, the delay management discussed here does not require the use of additional node positioning and timing techniques (such as using GPS) to synchronize message delivery between the nodes. Rather than rely on a separate system (such as GPS timing references) to determine the timing delay between each of the nodes, the system and methods described herein provide a substantially simplified means of determining signal path delays between each of the remote nodes and a host node.

The delay management technique described herein is topology independent. The delay management technique is applicable to a wide range of network topologies, such as star, tree, and daisy-chained network configurations, and combinations thereof Moreover, this delay management is medium-independent, and functions on a plurality of network infrastructures, such as wireless, free space optics, millimeter wave, twisted pair, coaxial, optical fiber, hybrid fiber, and suitable combinations thereof.

are block diagrams of embodiments of a communication network. Each ofshows a different embodiment of a communication network. The various embodiments are labeled communications networkA through communications networkB. It is understood that aspects of these embodiments can be combined together to create additional embodiments sharing features from any combination of the embodiments.

is block diagram of one exemplary embodiment of a communications network, labeled communications networkA. The communications networkA represents a point-to-multipoint communications network that comprises a base station, a host noderesponsive to the base station, and remote nodes-to-M in communication with the host node. The host nodecomprises a host base station interfaceand a host transport interfaceresponsive to a host node processor. Each of the remote nodes(such as remote nodes-to-M) comprises a remote transport interface(such as remote transport interface-to-M) and an RF to digital interface(such as RF to digital interface-to-M), both responsive to a remote node processor(such as remote node processor-to-M). Each of the RF to digital interfaces(such as RF to digital interface-to-M) is further responsive to an antenna port(such as antenna port-to-M).

In some embodiments, each host node processorand remote node processoris configured to execute software or firmware (not shown) that causes the host node processorand/or the remote node processorto carry out various functions described herein. The software comprises program instructions that are stored (or otherwise embodied) on an appropriate non-transitory storage medium or media (not show) such as flash or other non-volatile memory, magnetic disc drives, and/or optical dist drives. At least a portion of the program instructions are read from the storage medium by host node processorand/or remote node processorfor execution thereby. The storage medium on or in which the program instructions are embodied is also referred to here as a “program product”. In some embodiments, the storage medium is local to each host node processorand/or remote node processor. In other embodiments, the storage medium is a remote storage medium (for example, storage media that is accessible over a network or communication link) and/or a removable media. In some embodiments, each host node processorand/or remote node processoralso includes suitable memory (not shown) that is coupled to host node processorand/or remote node processorfor storing program instructions and data.

In some embodiments, each host base station interfaceand each RF to digital interfaceis implemented with a Digital/Analog Radio Transceiver (DART board) commercially available from ADC Telecommunications, Inc. of Eden Prairie, Minn. as part of the FlexWave™ Prism line of products. The DART board is also described in U.S. patent application Ser. No. 11/627,251, assigned to ADC Telecommunications, Inc., published in U.S. Patent Application Publication No. 2008/01101482, and incorporated herein by reference. In other embodiments, each host base station interfaceand each RF to digital interfaceis implemented with a plurality of DART boards, where one DART board is used for each port (such as D, D, D) at a host nodeor a remote node. In other embodiments, different ratios of DART boards to ports can be used. In other embodiments, some of the host base station interfacesdo not convert between analog and digital and instead receive digital signals directly from the base station. In these embodiments, the digital signals may be reframed, converted to a different frequency, or manipulated in other ways at host base station interfaces, even though there is no conversion from analog RF spectrum to digitized RF spectrum.

In one embodiment, each host transport interfaceand each remote transport interfaceis implemented with a Serialized RF (SeRF board) commercially available from ADC Telecommunications, Inc. of Eden Prairie, MN as part of the FlexWave™ Prism line of products. The SeRF board is also described in U.S. patent application Ser. No. 11/627,251, assigned to ADC Telecommunications, Inc., published in U.S. Patent Application Publication No. 2008/01101482, and incorporated herein by reference. In other embodiments, each host transport interfaceand each remote transport interfaceis implemented with a plurality of SeRF boards, where one SeRF board is used for each port (such as T, T, T) at a host nodeor a remote node.

In one embodiment, the host node processorand each remote node processorare programmable processors, such as a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a field-programmable object array (FPOA), or a programmable logic device (PLD). It is understood that the networkA is capable of accommodating any appropriate number of remote nodesas described above in communication networkA. In some embodiments, communication networkA includes fewer remote nodesthan those shown in. In other embodiments, systemA includes more remote nodesthan those shown in.

The host nodeand the remote nodesare communicatively coupled by a plurality of signal paths in a tree-and-branch network configuration representing a plurality of levels. In the example embodiment of communication networkA shown in, the tree-and-branch network configuration further includes signal switchesand. Each of the signal paths illustrated inare at least one of an electrical link, an optical fiber link, and a wireless transport link (such as millimeter wave, free space optics, or suitable combinations thereof), providing a medium-independent network architecture. It is understood that additional network configurations (such as a hub and spoke, a common bus, and the like) are also contemplated.

The host base station interfaceand each of the RF to digital interfacesinclude ports D, D, and D. The ports D, D, and Dare considered representative of a plurality of signal interference connections (such as RF, Ethernet, and the like) for the host base station interfaceand each of the RF to digital interfaces. In some embodiments, the host base station interfaceconverts between analog RF spectrum received from the base stationand digitized spectrum that is communicated with the remote nodes. In other embodiments, the host base station interfacecommunicated digitized spectrum or signals with the base station. In these embodiments, while the digitized spectrum or signals communicated with the base stationare not converted between analog and digital, the framing of the digitized spectrum or signals may need to be converted between the digitized spectrum or signals communicated with the base stationand the digitized spectrum communicated with the remote nodes.

Similarly, the host transport interfaceand each of the remote transport interfacesinclude ports T, T, and T. The ports T, T, and Tare considered representative of a plurality of transport interface connections for the host transport interface. Each of the remote transport interfacesprovide an appropriate signal conversion (such as a digital to serial or serial optical fiber) for each of the remote nodesand the host nodeof the communication networkA. It is understood that the ports Dto Dand Tto Tshown inare not to be considered limiting the number of signal interface and transport ports contemplated by the system discussed here (e.g., the communication networkA is capable of accommodating any appropriate number of instances of signal interface and transport ports).

Each remote node(such as remote node-to-M) introduces one or more intrinsic processing delays. For example, the remote transport interfacesincludes a first intrinsic processing delay when passing signals between the transport interface connections Tand T(commonly referred to as a “fiber-to-fiber” delay in this example). Similarly, each of the RF to digital interfacesincludes a second intrinsic processing delay for converting signals between digital and RF. In some instances, the intrinsic processing delays in RF to digital interfaceare asymmetrical. This means that the intrinsic processing delay for upstream signals (signals going to the host node) and the intrinsic processing delay for downstream signals (signals coming from the host node) are different. In one embodiment, the various intrinsic processing delays are embedded in each of the remote node processors(such as remote node processor-to-M) for use in establishing the requested delay for the node.

In operation, communication networkA implements an end-to-end pinging process to determine the signal path delay between each port (such as D, D, and D) in the RF to digital interfaceat each remote nodeand a corresponding host base station interfaceat the host node. In this end-to-end pinging process, each port in the RF to digital interfaceat each remote nodein the communication networkA discovers its signal path delay back to a corresponding port in the host base station interfaceof the host nodeby sending a ping message to the host nodethrough the communication networkA. The corresponding port in the host base station interfaceof the host nodereturns the ping message to the corresponding port of the RF to digital interfaceof the pinging remote node. The ping message is sent along a path between the pinging remote nodeand the host node. A particular pinging remote nodemay be directly coupled with the host node, such as with remote nodes-,-, and-.

A particular pinging remote nodemay also have other remote nodesintervening between itself and the host node, such as with remote node-that has remote node-intervening; remote node-that has both remote node-and-intervening; remote node-that has remote node-intervening; remote node-that has both remote nodes-and-intervening; remote node-that has remote node-intervening; and remote node-that has both remote node-and-intervening. In addition, a particular pinging remote nodemay also have other components, or a combination of other components and other remote nodes, intervening between itself and the host node, such as remote node-that has signal switchesandand remote node-intervening; and remote node-M that has remote node-, signal switchesand, and remote node-intervening. In other embodiments, any number of intervening remote nodesor other components (such as signal switches, etc.) may be intervening between a particular remote nodeand the host node.

The signal path delay between a pinging port of the RF to digital interfaceof a particular remote nodeis calculated based on the elapsed round-trip ping time between sending a ping message from the pinging port of the RF to digital interfaceof the remote nodeand receiving back a corresponding reply ping message from the corresponding port of the host base station interfaceof the host node. In some example embodiments, the signal path delay for a particular remote nodeis calculated to be this round-trip ping time. In other example embodiments, the signal path delay for a particular remote nodeis calculated to be a fraction of this round-trip ping time, such as one-half of the round-trip ping time. In other example embodiments, the signal path delay for a particular remote nodeis calculated from the round-trip ping time in other ways. While the precise method of calculation may vary from one embodiment to another, it is desirable that the method of calculation is consistent and defined for all remote nodesin the communication networkA so that the signal path delay values for each remote nodecan be properly used to adjust the delay associated with each remote nodein the communication networkA.

Thus, each signal path delay between each pinging port of the RF to digital interfaceof each remote nodeand the corresponding port of the host base station interfaceof the host nodeis calculated to represent the entire delay between the pinging port of the RF to digital interfaceof the particular remote nodeand the corresponding port of the host base station interfaceof the host node, including any transport delay, internal processing delay, and other intrinsic processing delay present between the pinging port of the RF to digital interfaceof the pinging remote nodeand the corresponding port of the host base station interfaceof the host node. By calculating the end-to-end ping between each port of each RF to digital interfaceof each remote nodeand its corresponding port of the host base station interfaceof the host node, it is not necessary to factor in the internal processing delay (or other intrinsic delay) at each intervening remote node between a particular pinging remote nodeand the host node. The end-to-end ping is computationally less intensive than other methods requiring computation and aggregation of the delays associated with each hop between nodes in the network. The current system and method allow a reduction of resource usage and lower overhead at each node in the communication networkA.

Some embodiments of the communication networkA implement simulcast, where at least one of the ports of the host base station interfaceof the host nodecorresponds to a plurality of ports of at least one RF to digital interface. For example, in some embodiments, at least one of the ports of the host base station interfaceof the host nodecorresponds to both a first port in a first RF to digital interfacein a first remote node(such as RF to digital interface-of remote node-) and a second port in a second RF to digital interfacein a second remote node(such as RF to digital interface-of remote node-or any of the other RF to digital interfacesof any of the other remote nodes). In these type of simulcast configurations, one port of the host base station interfaceof the host nodecommunicates identical digitized spectrum in the forward link with a plurality of ports at a plurality of RF to digital interfacesat a plurality of remote nodes. In these type of simulcast configurations, the plurality of ports at the plurality of RF to digital interfacesat a plurality of remote nodescommunicate digitized spectrum in the reverse path that is aggregated and received at the single port of the host base station interfaceof the host node. In some embodiments, the reverse path signal is aggregated through a series of summations. The actual method of aggregation of the simulcast may be done in various ways while still utilizing the methods and systems of end-to-end determination of delay described herein.

In some embodiments, it is necessary to add an internal processing delay and/or some other type of intrinsic delay associated with the particular pinging remote nodeand the host node. Specifically, the host node may have some internal processing delay associated with its host base station interface(or any other internal processing delay not accounted for by the round-trip ping time) that can be used with the round-trip ping time and any other intrinsic delays that are not accounted for by the round-trip ping time to determine the signal path delay. In addition, the particular pinging remote node may have some internal processing delay associated with its RF to digital interfaceor the respective antenna port(or any other internal processing delay not accounted for by the round-trip ping time) that can be used with the round-trip ping time and any other intrinsic delays that are not accounted for by the round-trip ping time to determine the signal path delay.

The remote nodes(such as-to-M) use the signal path delay calculated through this process to control the overall delay selected for each RF to digital interfaceof each remote node. For example, a total delay for each RF to digital interfaceof each remote node may be established during network installation. Each RF to digital interfaceof each remote node sets the amount of delay that it introduces into signals based on the signal path delay learned using the above-described process. Thus, a common time base is established for RF to digital interfacesin the remote nodesin communication networkA.

In addition to calculating signal path delay, the ping messages may be used to verify integrity of the round-trip path. Both ping messages sent from RF to digital interfacesof remote nodesand reply ping messages sent from host base station interfacesof host nodesmay be protected and validated by a cyclic redundancy check (CRC). In some embodiments, messages received at either host base station interfacesof the host nodeor RF to digital interfacesof remote nodeswith invalid CRCs are ignored. Specifically, when a ping message received at a host digital interfaceof a host nodeis identified as having an invalid CRC, the host base station interfaceof the host nodewill not send a reply ping message in response. Similarly, when a ping message received at a RF to digital interfaceof a remote nodeis identified as having an invalid CRC, the RF to digital interfaceof the remote nodeignores the invalid message. In some embodiments, there may be other types of validity checks used to validate the integrity of the messages transmitted through the communication networkA.

In addition, due to the simulcast nature of the communication networkOOA, a first reverse path ping message initiated by a RF to digital interfaceof one of the remote nodes(such as RF to digital interface-of remote node-) might collide with a second reverse path ping message initiated by another RF to digital interfaceof another one of the remote nodes(such as RF to digital interface-of remote node-). A collision between two ping messages may cause both messages to be corrupted so that neither ping message is received intact at a host base station interfaceof a host node(such as host base station interface-of host node-). The corrupted message received at the host base station interfaceof the host nodemay include bits from both the first and second reverse path ping messages. Such a corrupted message will be identified as invalid by the CRC performed by the host base station interfaceof host nodeand will not be replied to by the host base station interfaceof host node.

To detect and recover from a collision, an embodiment of communication networkA may include configuration of each RF to digital interfaceat each remote nodeto detect whether or not it has received a valid ping reply message from the replying host digital interfaceof the replying host nodein response to its initial ping message within a predefined amount of time. If a ping reply message is received at the pinging RF to digital interfaceof the pinging remote nodebefore expiration of a predefined response and the ping message both: (1) has a valid CRC; and (2) corresponds to the pinging RF to digital interfaceof the pinging remote node, then the round-trip delay and signal path delay are calculated. Alternatively, if no ping reply message that both (1) has a valid CRC and (2) corresponds to the pinging RF to digital interfaceof the pinging remote nodeis received at the pinging RF to digital interfaceof the particular remote node, then the ping message is resent when the next ping trigger occurs. Ping triggers occur at pseudo-random time intervals. The ping trigger interval may be determined at each pinging remote node based on a pseudo-random back-off algorithm to minimize the chance of a collision between other upstream messages.

While the detection, timeout, retry cycle above could repeat indefinitely, some embodiments of communication networkA may further calculate how many times a particular ping message has been sent from a pinging RF to digital interface of a pinging remote nodewithout a valid corresponding reply ping message having been received. If the particular ping message has been resent by the pinging RF to digital interfaceof the pinging remote nodeover a predetermined number of times without having received a valid corresponding reply ping message, then a path integrity alarm may be reported at the particular pinging remote nodein the communication networkA indicating that something is wrong with the data path between the pinging RF to digital interfaceof the pinging remote nodeand the corresponding host base station interfaceof the corresponding host node. This path integrity alarm may alert a technician to a potential data path error so that the technician can investigate and correct the issue. The number of messages that must fail before the remote node reports a path integrity alarm may be predetermined when the communication networkA is deployed, but may also be adjusted later. In other embodiments, a timeout period is used instead of a ping trigger.

In addition to calculating the end-to-end ping and verifying the integrity of the round-trip paths, the ping messages may also be used to mute and un-mute the transmission and reception from an antenna coupled to a port of an RF to digital interfaceon a remote node. In some embodiments, a certain number of valid ping messages need to be received back at a pinging RF to digital interfaceof a remote nodebefore the pinging RF to digital interface un-mutes a port coupled to the associated antenna port, allowing transmission and reception of a particular band through the data path between the port of the RF to digital interface(such as port Dof RF to digital interface-of remote node-) and a host base station interface(such as port Dof host base station interfaceof host node) coupled to a service provider interface of base station(such as service provider interfaceof base station-). This features ensures the integrity of the path and compatibility between the pinging RF to digital interfaceand the host base station interfacebefore un-muting the communications.

is block diagram of another exemplary embodiment of a communications network, labeled communications networkB. The communications networkB represents a multipoint-to-multipoint communications network that shares many components with communications networkA shown inand described above. The primary distinction between communications networkB and communication networkA is that communication networkB includes two or more host nodes(such as host node-and host node-) coupled with two or more base stations(such as base station-and base station-). In communications networkB, a single remote nodecan be coupled to a plurality of host nodes(such as remote node-which is connected to both host node-and host node-).

In embodiments having two host nodes, a single remote unit may have two RF to digital interfaces, where one is associated with a host base station interfacein one host node(such as host base station interface-of host node-) and the other is associated with a different host base station interfacein another host node(such as host base station interface-in host node-). In other embodiments having two hosts nodes, one port of a RF to digital interfaceof a remote node (such as Dof RF to digital interface-of remote node-) may be associated with one port of one host base station interfacein a host node(such as Dof host base station interface-of host node-).

In embodiments where each remote node has multiple RF to digital interfaces, ping messages are sent for each of the RF to digital interfacesto a host nodehaving a host digital interfaceassociated with the respective RF to digital interface. In some embodiments where a remote unitis communicatively coupled to a plurality of host nodes, one port of RF to digital interfaceof the remote unit(such as D1 of RF to digital interface-of remote node-) may be associated with a host base station interfaceof one host node(such as host base station interface-of host node-) while another port of RF to digital interfaceof the remote node(such as Dof RF to digital interface-of the remote node-) may be associated with a host base station interfaceof another host node(such as host base station interface-of host node-).

An additional distinction between communications networkB and communications networkA is that communication networkB includes analog remote nodes(such as analog remote nodes-and-M coupled to remote node-). In embodiments implementing analog remote nodes, intermediate frequencies (IF) may be used to transmit multiple bands across a single analog medium. For example, a remote node(such as remote node-) includes an analog IF to digital interface(such as analog IF to digital interface-) that converts between digitized RF spectrum received from the associated host nodeand an analog IF frequency sent across the analog medium to an analog remote node(such as analog remote node-). In some embodiments, each analog remote node(such as analog remote node-through analog remote node-M) includes an analog IF transport interface(such as analog IF transport interface-through analog IF transport interface-M) and an IF to RF interface(such as IF to RF interface-through IF to RF interface-M) responsive to an analog remote node processor(such as analog remote node processor-through analog remote node processor-M). Each of the IF to RF interfaces(such as IF to RF interface-to-M) is further responsive to an antenna port(such as antenna port-to-M).

As is shown in the example embodiment shown in, a plurality of analog remote nodes can be daisy chained off from a remote node in the communications networkB. In other embodiments, other network topologies can be used in both the digital and analog portions of the communications networkB. In the example embodiment shown in, the end-to-end ping is only calculated in the digital portions of the networkB. In some embodiments, an analog IF to digital interfaceof a remote node(such as analog IF to digital interface-of remote node-) calculates an end-to-end ping to a host base station interfaceof a host node(such as host base station interface-of a host node-) using the methods described herein. The remote node-can then add in some intrinsic delay to account for the delay through the various portions of the analog system (such as to IF to RF interface-of analog remote node-and IF to RF interface-M of analog remote node-M). In this way, the end-to-end delay between the analog nodes can also be estimated.

In other embodiments, the additional delay in the analog portion of the communications networkB is disregarded because it is insubstantial compared to the delay introduced by the digital portion of the communication networkB. This may be the case because the distances between the remote nodesand the host nodesin the digital domain is much greater than the distances between the analog remote nodesand the remote nodesthey are connected to (such as remote node-).

is a block diagram of another exemplary embodiment of a communications network, labeled communications networkC. The communications networkC represents a communications network that includes the host node-and the remote node-. Each of host node-and remote node-include the components describe above. In some embodiments, additional remote nodesor other components lie between host node-and remote node-in optional intervening component section. In some embodiments, optional intervening component sectionincludes intervening remote nodes, signal switches, and physical links, such as optical fibers, coaxial cables, and wireless links. The communications networkC implements an end-to-end ping as described herein. The precise contents of the optional intervening component sectionis not particularly relevant to the end-to-end ping as long as the components in the optional intervening component sectionproperly forward any ping initiation messages and ping reply messages between the host node-and remote node-.

is a block diagram of a frameworkfor network applications. The frameworkcomprises multiple layers, discussed below, that provide hardware-related service to enable each node of the communication networkA to function as shown above with respect to(e.g., the host nodediscovers the plurality of remote nodesover the communication networkA). The frameworkcomprises an application layer, a network layer, a data link layer, and a physical layer. Each layer of the frameworkcompartmentalizes key functions required for any node of the communication networkto communicate with any other node of the communication network.

The physical layeris communicatively coupled to, and provides low level support for the data link layer, the network layer, and the application layer. In some embodiments, the physical layerresides on at least one of an optical fiber network, a coaxial cable network, and a wireless network. The physical layerprovides electronic hardware support for sending and receiving data in a plurality of operations from the at least one network application hosted by the host node. The data link layerprovides error handling for the physical layer, along with flow control and frame synchronization. The data link layerfurther includes a data frame sub-layer. The data frame sub-layercomprises a plurality of data frames transferred on the physical layer. Additional detail pertaining to the data frame sub-layeris further described below with respect to. The network layeris responsive to at least one programmable processor within the network(for example, the host node processoror at least one of the remote node processors). The network layerprovides switching and routing capabilities within the networkfor transmitting data between the nodes within the network. The application layeris responsive to at least one of a simple network management protocol (SNMP), a common management information protocol (CMIP), a remote monitoring (RM) protocol, and any network communications protocol standard suitable for remote monitoring and network management.

is a block diagram of an embodiment of the data frame sub-layerof, represented generally by the sub-layer. The sub-layercomprises at least one data frame(or optical fiber frame). Each data frameis composed of a plurality of slots organized into rows and columns as shown in. Each RF to digital interfaceof each remote nodeis assigned at least one timeslot in the reverse path to transmit digitized RF spectrum to a host base station interfaceof a host node. In addition, each RF to digital interfaceof each remote nodeis assigned at least one timeslot in the forward path to receive digitized RF spectrum from a host base station interfaceof a host node. In some embodiments, a single RF to digital interfaceis assigned multiple slots in the upstream and/or the downstream. Similarly, in some embodiments, a single host base station interfaceis assigned multiple slots in the upstream and/or downstream. In some embodiments, implementing simulcast in the forward path, a single host base station interfaceof a host nodemay transmit digitized RF spectrum in the downstream on at least one timeslot that is received at a plurality of RF to digital interfacesat a plurality of remote nodes. Similarly, in the reverse path, a plurality of RF to digital interfacesat a plurality of remote nodesmay transmit digitized RF spectrum in the upstream on the same timeslot, where the digitized RF spectrum is summed together or aggregated in some other way.

Each timeslot, such as example timeslot, is composed of an I sampleand a Q sample. In the example timeslot, both the I sampleand the Q sampleinclude 16 bits. In the example timeslot, the 16th bit of the I sample, bit, is used to transmit the ping messages. In some embodiments, a single bitis used in each timeslot of the data frameto transmit the ping messages. Thus, a ping message can span multiple slots in a frame and can also span across frames. In the embodiments shown in, where only one bit per timeslot is used to transmit the ping message, it may take multiple frames to transmit a single ping message.

For example, in some embodiments, the ping message contains approximatelybits, requiringslots for transmission. Thus, in an embodiment where an RF to digital interfaceis assigned one timeslot per row of the data frame, it would take five frames to transmit thebits of one ping message. Similarly, in an embodiment where an RF to digital interfaceis assigned two timeslots per row of the data frame, it would take two and a half frames to transmit thebits of one ping message. The combined bits representing the ping message spanning multiple frames are sometimes referred to as a ping message superframe.

An example embodiment of a ping message having 80 bits may include a number of elements. First, a frame header may require 8 bits. The frame header is used to frame the message and identify the message type. Example message types include (1) messages initiated from a remote RF to digital interfaceand directed toward an analog host base station interface, (2) messages initiated from a remote RF to digital interfaceand directed toward a digital host base station interface, (3) messages initiated from an analog host base station interfaceand directed toward a remote RF to digital interface, and (4) messages initiated from a digital host base station interfaceand directed toward a remote RF to digital interface. The digital host base station interfaceis discussed above as being used when the base station outputs a digital signal to the host nodeinstead of an RF signal.

Second, a time slot count may require 4 bits. The timeslot count is used to identify the number of timeslots the sending DART is programmed to. This timeslot count should agree between the RF to digital interfaceand the corresponding host base station interfaceand can be used to verify that the network is correctly configured and/or the integrity of the path the ping message is being sent on.

Third, a host base station interface ID may require 8 bits. The host base station interface ID is a unique identifier code for the host base station interfacethat may be inserted into the ping reply message by the host base station interface. The RF to digital interfaceat the pinging remote nodecan then verify that it is compatible with the type of the host base station interfacebased on the host base station interface ID received back in the ping reply message. If the RF to digital interfaceat the pinging remote nodeis not compatible with the type of host base station interfaceidentified in the host base station interface ID, the RF to digital interfacecan be muted and an alarm can be triggered to indicate a mismatch between the types of the pinging RF to digital interfacethe host base station interface.

Fourth, a unique path code may require 37 bits. The unique path code is a unique value that identifies the path between the RF to digital interfaceand the host base station interface. This unique value serves as a unique identifier for each RF to digital interfacein the system. In the example embodiment using a 37-bit path code, the systemcan have up to 8 levels of cascades between the host node and a RF to digital interface. In other embodiments, path codes of different lengths can also be used, enabling various sizes of networks and levels of cascades. In some embodiments, this unique path code is supplied to the RF to digital interfaceby the remote transport interfaceof the remote node.

In some embodiments, the unique path code includes a 4-bit host node ID number that identifies the host nodethat contains the corresponding host base station interface. In embodiments having a 4 bit host node ID number, there are only 16 options for host node ID numbers. If the host base station interfacereceives a ping message that has a host node ID number that does not match its own, then the message is ignored.

In some embodiments, the unique path code also includes a 3-bit host base station interface ID number that identifies the target host base station interfacewithin the host node. In some embodiments, the base station interface ID number also identifies a particular port within the host base station interfaceof the host node. In some embodiments, the base station interface ID number identifies a communication port, such as a low-voltage differential signaling (LVDS) port, of the target host base station interfacewithin the host node.

In some embodiments, the unique path code also includes abit fiber path ID that identifies the path between the host nodeand the remote node. This unique path code may be broken into nine 3-bit values. The first 3-bit value represents the number of levels minus one in the cascaded mesh. For example, a system that only contains a host and a remote would have “000” in this field. The next eight 3-bit values represent the fiber port number of each link in the cascade. In systems with fewer than eight levels, the corresponding 3-bits will be unused and set to “000”.