WO2009012614A1

WO2009012614A1 - Bi-directional amplifier for data over coax application

Info

Publication number: WO2009012614A1
Application number: PCT/CN2007/002229
Authority: WO
Inventors: Jinfei Yu; Hongming Gu; Junbiao Zhang; Xiangkun Ma
Original assignee: Thomson Licensing
Priority date: 2007-07-23
Filing date: 2007-07-23
Publication date: 2009-01-29
Also published as: CN101874382B; CN101874382A

Abstract

A disclosed bi-directional amplifier circuit allows the use of data over coaxial cable protocols (for example, MOCA) over existing and newly developed cable TV systems. Through the use of directional couplers on the AP side of the bi-directional amplifier, equal bi-directional power amplification can be achieved. According to a general aspect, an apparatus includes a bi-directional amplifier (1212) configured to amplify signals having a first direction and to amplify signals having a direction opposite the first direction. The apparatus also includes a bi-directional power detector (1202-1204) coupled to the bi-directional power amplifier so as (1) to detect power in a signal having the first direction before the signal having the first direction is amplified by the bi-directional power amplifier, and (2) to detect power in a signal having the opposite direction after the signal having the opposite direction is amplified by the bi-directional power amplifier.

Description

BI-DIRECTIONAL AMPLIFIER FOR DATA OVER COAX APPLICATIONS

Technical Field

The present principles relate to cable based broadband communication networks. More particularly, they relate to a bidirectional amplifier and method for implementing the same.

Background

Coaxial cable has been, and continues to be used to transmit data. One limitation to the use of Coaxial cable to transmit data using other transmission protocols is a lack of speed in transmission due to the constraints of the Coax cable and the limited bandwidth associated with the same. In cable networks, the use of time division duplex bi-directional amplifiers has been considered. However, generally these amplifiers cannot support the desired speed and other constraints .

SUMMARY According to a general aspect, an apparatus includes a bidirectional power amplifier unit configured to amplify signals having a first direction and to amplify signals having a direction opposite the first direction. The apparatus also includes a bi-directional power detector unit coupled to the bi- directional power amplifier unit so as (1) to detect power in a signal having the first direction before the signal having the first direction is amplified by the bi-directional power amplifier unit, and (2) to detect power in a signal having the opposite direction after the signal having the opposite direction is amplified by the bi-directional power amplifier unit. According to another general aspect of the present principles, an amplifier circuit includes a directional coupler having an input and an output. The circuit further includes a bi-directional power amplifier having a by-pass mode and having an input coupled to the output of the directional coupler and an output configured to be connected to a modem, wherein the input of the directional coupler is configured to be connected to an

Access point. The directional coupler is connected on the Access point side of the bi-directional power amplifier. The circuit includes a power detector connected to the directional coupler and configured to detect uplink and downlink power. The circuit includes a voltage comparator having an inverting and non- inverting input, each connected to the power detector. The circuit includes a voltage division network connected to the non- inverting input of the voltage comparator and configured to provide a pre-bias voltage to the voltage comparator. The circuit includes a switch connected to the voltage comparator and the bi-directional power amplifier. The switch is configured to change an operation state of the bi-directional power amplifier in response to signals received from the voltage comparator. According to another general aspect, a method includes monitoring the presence of an uplink or downlink signal at an access point side of a bi-directional amplifier within a bidirectional amplifier circuit. The method further includes switching the bi-directional amplifier to a transmit state when only a downlink signal is present. According to a further general aspect, an apparatus includes an element (s) for monitoring the presence of an uplink or downlink signal at an access point side of a bi-directional amplifier within a bi-directional amplifier circuit. The apparatus also includes an element (s) for switching the bi- directional amplifier to a transmit state when only a downlink signal is present. According to another general aspect, an amplifier circuit is intended for use with existing CATV systems, where the CATV systems include one or more cable distributions, each cable distribution having at least one CATV trunk amplifier. The amplifier circuit includes a bi-directional amplifier unit arranged in parallel with each CATV trunk amplifier on a cable distribution. The bi-directional amplifier unit enables the passage of data over coaxial (DOCA) protocols to operate on the CATV system without interfering with or causing losses to a TV signal carried on the CATV cable distributions.

According to another general aspect, a cable system includes at least one power splitter having at least one input connected to a CATV cable based television service provider and at least one input connected to a data over coaxial cable (DOCA) protocol system. The at least one power splitter has at least one cable distribution output. The cable system also includes a CATV trunk amplifier connected in series with the at least one cable distribution. The cable system also includes a bi-directional amplifier circuit connected in parallel to the at least one cable distribution around said CATV trunk amplifier.

According to another general aspect, a method includes detecting a signal, having a particular transmission direction, at a first side of a power amplifier. The method includes amplifying the detected signal having the particular transmission direction using the power amplifier. The method includes detecting a signal, having a transmission direction opposite the particular transmission direction, at the first side of the power amplifier. The method includes amplifying the detected signal having the opposite transmission direction using the power amplifier.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Even if described in one particular manner, it should be clear that implementations may be configured or embodied in various manners. For example, an implementation may be performed as a method, or embodied as an apparatus configured to perform a set of operations or an apparatus storing instructions for performing a set of operations. Other aspects and features will become apparent from the following detailed description considered in conjunction with the accompanying drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.l illustrates a simplified exemplary TDF access network architecture.

Fig. 2 illustrates the 802.11 MAC sublayer in OSI reference model . Fig. 3 illustrates an implementation of a TDF transmission entity in OSI reference model.

Fig. 4 illustrates an implementation of a communication mode entrance procedure.

Fig. 5 illustrates an implementation of a TDF super frame structure.

Fig. 6 illustrates an implementation of a registration procedure .

Fig. 7 illustrates an implementation of an unregistration procedure . Fig. 8 illustrates an implementation of an alive notification procedure.

Fig. 9 includes a system diagram that depicts an implementation of a TDF network.

Fig. 10 includes a block diagram of an implementation of an AP and a modem from Fig. 9. Fig. 11 is a high level diagram of an implementation of a system within which the present principles may be implemented.

Fig. 12 is a block diagram of an implementation of a bidirectional amplifier according to an aspect of the present principles .

Fig. 13 is a detailed block diagram of a bi-directional amplifier according to an implementation of the present principles .

Fig. 14 is a schematic diagram of an implementation of a bi- directional amplifier according to an aspect of the present principles .

Fig. 15 is a block diagram of a method according to an implementation of the present principles.

Fig. 16 is a block diagram of another method according to an implementation of the present principles.

DETAILED DESCRIPTION

In order to provide data service over existing coaxial cable TV system (CATV) , at least one implementation deploys a time divisional function (TDF) protocol compliant Access Point (AP) and stations (STAs) in the cable access network. The AP and STAs are connected via splitters in the hierarchical tree structure. In this way, the user at home can access the remote IP core network via the cable access network. The detailed network topology is illustrated as illustrated in Fig.l. As can be seen from Fig.l, in this typical access network infrastructure, there is a TDF protocol compliant AP which has one Ethernet Interface in connection with the IP core network, and one coaxial cable interface in connection with the cable access network. On the other end of the cable access network, there are TDF protocol compliant STAs, i.e. terminals, which connect with the cable access network via the coaxial cable interface and connect with the home LAN (Local Area Network) via the Ethernet interface.

According to at least one implementation, both TDF APs and STAs implement the protocol stack separately in logically link control sublayer, MAC sublayer and physical layer, according to 802.11 series specifications. However, in the MAC sublayer, the TDP APs and STAs replace the 802.11 frame transmission entity with TDF frame transmission entity. So, the MAC sublayer for TDF APs and STAs is composed of 802.11 frame encapsulation/decapsulation entity and TDF frame transmission entity, while MAC sublayer for 802.11 compliant APs and STAs consists of 802.11 frame encapsulation/decapsulation entity and 802.11 frame transmission entity. For an integrated AP and STA, the TDF frame transmission entity and 802.11 frame transmission entity may co-exist at the same time, to provide both 802.11 and TDF functionality. The switch between the two modes can be realized by manually or dynamically configuration.

Basic approach

The main idea of the TDF protocol is to transmit IEEE802.il frames in the coaxial cable media instead of over the air. The purpose of utilizing the IEEE802.il mechanism is to make use of the mature hardware and software implementation of 802.11 protocol stacks.

The main feature of TDF is its unique medium access control method for transmitting IEEE802.il data frames. That is, it doesn't utilize the conventional IEEE802.il DCF (Distributed Coordination Function) or PCF (Point Coordination Function) mechanism to exchange MAC frames, which include MSDU (MAC Service Data Unit) and MMPDU (MAC Management Protocol Data Unit) . Instead, it uses time division access method to transmit MAC frames. So the TDF is an access method which defines a detailed implementation of frames transmission entity located in MAC sublayer.

For the purpose of comparison, here we illustrate IEEE802.il MAC sublayer protocol in the OSI reference model as shown in the Fig.2. While the exact location for TDF protocol in the OSI reference model is illustrated in the Fig.3.

Communication mode entrance procedure Currently, there are two communication modes proposed for the TDF compliant stations described as below. One is the standard IEEE802.il operation mode, which obeys to the frame structure and transmission mechanism defined in IEEE802.il series standard; the other is in TDF operation mode, the detailed information about which will be discussed in the following paragraphs. The strategy of determining entering into which operation mode when a TDF STA is started is indicated in the Fig.4. Once a TDF STA receives a synchronization frame from an AP, it is enabled to entering into TDF mode, if there is no synchronization frame received within a preset timeout, then the TDF STA remains or shifts into IEEE802.il mode.

TDF protocol functional description Access method The physical layer in a TDF station may have multiple data transfer rate capabilities that allow implementations to perform dynamic rate switching with the objective of improving performance and device maintenance. Currently, TDF station may support three types of data rates: 54Mbps, 18Mbps and 6Mbps . The data service is provided mainly in 54Mbps data rate. When there are some problems for a station to support 54Mbps data transmission, it may temporarily switch to 18Mbps data rate. The βMbps data rate operation mode is designed for the purpose of network maintenance and station debugging. The data rate may be configured statically before a TDF station enters the TDF communication procedure, and remain the same during the whole communication process. On the other hand, the TDF station may also support dynamical data rate switch during the service. The criteria for the data rates switch may be based on the channel signal quality and other factors .

The fundamental access method of TDF protocol is Time Division Multiple Access (TDMA) , which allows multiple users to share the same channel by dividing it into different time slots, The TDF STAs transmit in rapid succession for uplink traffic, one after the other, each using their own time slot in a TDF super frame assigned by the TDF AP. For downlink traffic, the STAs share the channels, and select the data or management frames targeting to them by comparing the destination address information in the frames with their address. Fig.5 illustrates an example of TDF super frame structure and the time slots allocation for a typical TDF super frame when there are m STAs which simultaneously compete for the uplink transmission opportunity.

As shown in Fig.5, there are fixed tdfTotalTimeSlotNumber timeslots per TDF super frame, which is composed of one synchronization time slot used to send clock synchronization information from TDF AP to TDF STAs; one contention time slot used to send registration request for uplink time slot allocation; tdfUplinkTimeSlotNumber uplink time slots used by the registered TDF STAs to send data and some management frames to TDF AP one after another; and tdfDownlinkTimeSlotNumber downlink time slots used by TDF AP to transmit data and registration response management frames to the modems. Except the synchronization time slot, all other time slots, which are named as common time slot, have same duration whose length equals with tdfCommonTimeSlotDuration. The value of tdfCommonTimeSlotDuration is defined to allow the transmission of at least one largest IEEE802.il PLCP (physical layer convergence protocol) protocol data unit (PPDU) in one normal time slot for the highest data rate mode. The duration of synchronization time slot, tdfSyncTimeSlotDuration, is shorter than that of the common time slot, because the clock synchronization frame, which is transmitted from TDF AP to TDF STA in this time slot, is shorter than the 802.11 data frame.

As a result, the duration of one TDF, super frame, defined as tdfSuperframeDuration, can be calculated by: tdfSuperframeDuration = tdfSyncTimeSlotDuration + tdfCommonTimeSlotDuration * (tdfTotalTimeSlotNumber - 1)

The relationship between tdfTotalTimeSlotNumber, tdfUplinkTimeSlotNumber and tdfDownlinkTimeSlotNumber satisfies the following equality: tdfTotalTimeSlotNumber = tdfUplinkTimeSlotNumber + tdfDownlinkTimeSlotNumber + 2

Furthermore, the number of allocated uplink time slots for the TDF STAs in a TDF super frame may change from one to tdfUplinkTimeSlotThreshold. Accordingly, the available downlink time slots in a TDF super frame may change from (tdfTotalTimeSlotNumber-2) to (tdfTotalTimeSlotNumber-2- tdfMaximumUplinkTimeSlotNumber) . Every time when there is one TDF STA which asks for an uplink time slot, the TDF AP will deduce one or more time slots from the available downlink time slots, and then allocate these time slots to the TDF STA, as long as the uplink time slots number won't exceed tdfMaximumUplinkTimeSlotNumber after that. The value of tdfMaximumUplinkTimeSlotNumber may vary in different implementations. But it must be carefully chosen so that there is at least one downlink time slot available for an associated TDF STA in order to guarantee the QoS of data service. Furthermore, all successive time slots that will be used by the same TDF STA or AP for same direction transmission can be merged to send MAC frames continuously to avoid the wastes at the edge of these time slots caused by the unnecessary conversion and guarding.

In current implementation, the tdfCommonTimeSlotDuration is about 300us, which is enough for the TDF STA to transmit at least one largest 802.11 PPDU in one common time slot for 54M mode, and there are total 62 time slots per TDF super frame. In these time slots, there are 20 uplink time slots and 40 downlink time slots in this way. When there are 20 STAs, each TDF STA can be guaranteed that it has access to 680kbps uplink data rate and shares 30Mbps (40 continuous time slots) downlink data rate; when there are 30 STAs, each TDF STA can be guaranteed that it has access to 680kbps uplink data rate and shares 22.5Mbps (30 continuous time slots) downlink data rate. The tdfMaximumUplinkTimeSlotNumber is 30. Finally, the value of tdfSuperframeDuration, which is the total duration of 61 common time slots and one synchronization time slot, is about 18.6ms and it can be defined to different value for different usage. For example, if there is only 1 TDF STA, it can be guaranteed that it has 4 time slots to achieve about 18Mbps uplink data rate and own 18Mbps (4 continuous time slots) downlink data rate. In this way, the value of tdfSuperframeDuration, which is the total duration of nine data timeslots and one synchronization timeslot, is about 4ms. Frame formats

In the 802.11 specification, three major frame types exist. Data frames are used to exchange data from station to station. Several different kinds of data frames can occur, depending on the network. Control frames are used in conjunction with data frames to perform area clearing operations, channel acquisition and carrier-sensing maintenance functions, and positive acknowledgement of received data. Control and data frames work in conjunction to deliver data reliably from station to station. More specifically, one important feature for the data frames exchanging is that there is an acknowledgement mechanism, and accordingly an Acknowledgement (ACK) frame for every downlink unicast frame, in order to reduce the possibility of data loss caused by the unreliable wireless channel. Finally, management frames perform supervisory functions: they are used to join and leave wireless networks and move associations from access point to access point . However, in TDF system, because TDF STAs passively waits for the Synchronization frame from TDF AP to find the targeting TDF AP, there is no need for the classical Probe Request and Probe Response frames. Furthermore, the frames are exchanged in coaxial cable instead of in the air, so it isn't necessary to define RTS and CTS frames to clear an area and prevent the hidden node problem, and to define ACKs frames to ensure the reliability of delivery of data frames.

So, in TDF protocol, we only use some useful 802.11 MSDU and MMPDU types for data over coaxial cable scenario. For example, we utilize the data subtype in data frame types, which is used to encapsulate the upper layer data and transmit it from one station to another. Furthermore, to cope with clock synchronization requirement in TDF system, we define a new kind of management frame—Synchronization frame; and to realize the functionality of uplink time slot request, allocation and release, we defines other four kinds of management frames that are Registration request, Registration response, Unregistration request and Alive notification.

To summarize it, we have defined four new subtypes in management frame type in TDF protocol. The following table defines the valid combinations of type and subtype added in TDF protocol. Table 1 shows valid type and subtype for TDF frames added in TDF protocol.

Table 1

TDF access procedure

TDF AP finding and clock Synchronization procedure

TDF protocol depends a great deal on the distribution of timing information to all the nodes. Firstly, the TDF STA listens to a Synchronization frame to decide if there is a TDF AP available. Once it enters the TDF communication procedure, it uses the Synchronization frame to adapt the local timer, based on which the TDF STA shall decide if it is its turn to send the uplink frames. At anytime, TDF AP is master and TDF STA is slave in synchronization procedure. Further, if it hasn't received any Synchronization frame from the associated AP for a predefined threshold period, which is defined as tdfSynchronizationCycle, the TDF STA will think that the AP has quit the service, and then it will stop the TDF communication process and start to look for any TDF AP by listening to the Synchronization frame again.

In the TDF system, all STAs associated with the same TDF AP shall be synchronized to a common clock. The TDF AP shall periodically transmit special frames called Synchronization that contains its clock information to synchronize the modems in its local network. Every TDF STA shall maintain a local timing synchronization function (TSF) timers, to ensure it is synchronized with the associated TDF AP. After receiving a Synchronization frame, a TDF STA shall always accept the timing information in the frame. If its TSF timer is different from the timestamp in the received Synchronization frame, the receiving TDF STA shall set its local timer according to the received timestamp value. Further, it may add a small offset to the received timing value to account for local processing by the transceiver.

Synchronization frames shall be generated for transmission by the TDF AP once every TDF super frame time units and sent in the Sync time slot of every TDF super frame.

Registration procedure

Fig.6 illustratively describes the whole procedure of registration. Once a TDF STA has acquired timer synchronization information from the Synchronization frame, it will learn when time slot 0 starts. If a TDF STA doesn't associate with any TDF AP, it will try to register with the specific TDF AP, which sent the Synchronization frame, by sending Registration request frames to TDF AP during the contention time slot, which is the second time slot in a TDF super frame. The duration of contention time slot, which equals with tdfCommonTimeSlotDuration, and the Registration request frame structure should be carefully designed to allow for sending at least tdfMaximumUplinkTimeSlotNumber Registration request frames in one contention time slot. Based on the design, the contention time slot is divided into tdfMaximumUplinkTimeSlotNumber same length sub-timeslots .

As soon as it finds the targeting TDF AP, a TDF STA will choose one sub-timeslot in the contention time slot to send Registration request frame to the TDF AP according to the following method: A. Every time when it is allocated an uplink time slot, a TDF STA will store the allocated uplink time slot number, defined as tdfAllocatedUplinkTimeSlot, which indicates the time slots' location in the whole uplink time slots pool and ranges from 1 to tdfMaximumUplinkTimeSlotNumber. B. The TDF AP should try its best to allocate same uplink time slot to the same TDF STA every time when it asks for an uplink time slot.

C. When it is time to decide to choose which sub- timeslot to send Registration request frame, if there is a stored tdfAllocatedUplinkTimeSlot value, the TDF STA will set the sub-timeslot number as same as tdfAllocatedUplinkTimeSlot ; if there isn't such a value, the TDF STA will randomly choose one sub-timeslot in the tdfMaximumUplinkTimeSlotNumber available sub-timeslots. It will send the Registration request frame to the TDF AP in the randomly chosen sub-timeslot. The purpose for this kind of operation is to reduce the chance of collision when there are many STAs start at the same time and try to register with the same TDF AP simultaneously.

The TDF STA will list all data rates it supports at that time and also carry some useful information such as the received signal Carrier/Noise ratio in the Registration request frame. It may send several successive Registration request frames with different supported data rates, starting from the highest data rate. After sending out the frame, the TDF STA will listen for the Registration response frames from the TDF AP.

After receiving a Registration request frame from a TDF STA, based on the following method, the TDF AP will send different kinds of Registration response frames back to the TDF STA in the downlink time slots:

A. If the already allocated uplink time slots equals with tdfMaximumϋplinkTimeSlotNumber, the TDF AP will put an uplinkTimeSlotUnavailable indicator in the frame body.

B. If the TDF AP doesn't support any data rates listed in the supportedDataratesSet in the Registration request management frame, the TDF AP will put an unsupportedDatarates indicator in the frame body.

C. If there are uplink timeslots available to allocate and common data rates that both the TDF AP and TDF STA can support, the AP will allocate one uplink time slot and choose a suitable common data rates according to some information such as Carrier/Noise ratio in the STA' s Registration request frame, and then send a Registration response frame to the TDF STA. In the frame body, the information about the allocated uplink time slot and the chosen data rate will be contained. After a successful registration process, the TDF STA and TDF AP will reach an agreement on which uplink time slot and data rate to use.

Fragmentation/defragmentation procedure

In TDF protocol, the time slot duration for the transmission of MSDU is fixed as tdfCommonTimeSlotDuration. In some data rates, when the MSDU' s length is more than a threshold, it is impossible to transmit it in a single time slot. So when a data frame for uplink transmission is longer than the threshold, which is defined as tdfFragmentationThreshold and varies depending on different data rates, it shall be fragmented before scheduled for transmitting. The length of a fragment frame shall be an equal number of octets (tdfFragmentationThreshold octets) , for all fragments except the last, which may be smaller. After fragmentation, the fragmented frames shall be put into the outgoing queue for transmission to the TDF AP. This fragmentation procedure may run in the TDF frame transmission entity or in the upper layer by using the tdfFragmentationThreshold dynamically set in the TDF frame transmission entity.

At the TDF AP end, each fragment received contains information to allow the complete frame to be reassembled from its constituent fragments. The header of each fragment contains the following information that is used by the TDF AP to reassemble the frame:

A. Frame type

B. Address of the sender, obtained from the Address 2 field

C. Destination address D. Sequence Control field: This field allows the TDF AP to check that all incoming fragments belong to the same MSDU, and the sequence in which the fragments should be reassembled. The sequence number within the Sequence Control field remains the same for all fragments of a MSDU, while the fragment number within the Sequence Control field increments for each fragment.

E. More Fragments indicator: Indicates to TDF AP that this is not the last fragment of the data frame. Only the last or sole fragment of the MSDU shall have this bit set to zero. All other fragments of the MSDU shall have this bit set to one.

The TDF AP shall reconstruct the MSDU by combining the fragments in order of fragment number subfield of the Sequence Control field. If the fragment with the More Fragments bit set to zero has not yet been received, the TDF AP will know that the frame is not yet complete. As soon as the TDF AP receives the fragment with the More Fragments bit set to zero, it knows that no more fragments may be received for the frame.

The TDF AP shall maintain a Receive Timer for each frame being received. There is also an attribute, tdfMaxReceiveLifetime, which specifies the maximum amount of time allowed to receive a frame. The receive timer starts on the reception of the first fragment of the MSDU. If the receive frame timer exceeds tdfMaxReceiveLifetime, then all received fragments of this MSDU are discarded by the TDF AP. If additional fragments of a directed MSDU are received after its tdfMaxReceiveLifetime is exceeded, those fragments shall be discarded.

Uplink transmission procedure After receiving the Registration response frame from the TDF AP, the TDF STA will analyze the frame body to see if it is granted an uplink time slot. If not, it will stop for a while and apply for the uplink time slot later. If yes, it will start to transmit uplink traffic during the assigned time slot using the data rate indicated in the Registration response frame. At the beginning of the uplink transmission during the assigned timeslot, the TDF STA will send the first frame in its outgoing queue to the TDF AP if there is at least one outgoing frame in the queue. After that, the TDF STA will check the second uplink frame' s length and evaluate if it is possible to send it during the remaining duration in the assigned timeslot. If not, it will stop the uplink transmission procedure and wait for sending it in the assigned timeslot during the next TDF super frame. If yes, it will immediately send the second frame to the destination TDF AP. The sending procedure will continue to run in this way until the assigned timeslot has ended, or there isn't any uplink frame to transmit.

Downlink transmission procedure

In the whole TDF communication procedure, the total downlink time slots number may change dynamically due to the changing associated STAs number. When the TDF AP prepares to send frames to the associated STAs, it will compare the time left in the remaining downlink time slots with the duration needed for transmitting the specific downlink frame using the agreed data rate. Then based on the result, it will decide if the frame should be transmitted with the specific data rate during this TDF super frame. Furthermore, TDF AP doesn't need to fragment any downlink frames.

When it isn't time for the associated STA to send uplink traffic, the STA will always listen to the channel for the possible downlink frames targeting to it. Unregistration procedure

As shown in Fig. 7 , if the TDF STA decides to quit the TDF communication procedure, it shall send an Unregistration request frame to the associated TDF AP during its uplink time slot, in order to inform the TDF AP to release the allocated uplink time slot resource for it. After receiving the Unregistration request frame, the TDF AP will free the uplink time slot assigned for the TDF STA and put it into free time slots pool for the future use.

Alive notification procedure

Now with reference to Fig. 8, to release the resources as soon as possible when a TDF STA unexpectedly crashes or shuts down, the TDF STA must report its aliveness by sending an Alive notification frame periodically to TDF AP during its uplink time slot period. If there isn't any Alive notification frame for a predefined threshold period which is named as tdfAliveNotificationCycle, the associated TDF AP will think that the TDF STA has quit the service, and then release the uplink time slot allocated for the TDF STA, just like receiving an Unregistration request frame from the TDF STA.

In order to ensure coexistence and interoperability on multirate-capable TDF STAs, this specification defines a set of rules that shall be followed by all stations: A. The Synchronization frames shall be transmitted at the lowest rate in the TDF basic rate set so that they will be understood by all STAs.

B. All frames with destination unicast address shall be sent on the supported data rate selected by the registration mechanism. No station shall transmit a unicast frame at a rate that is not supported by the receiver station. C. All frames with destination multicast address shall be transmitted at the highest rate in the TDF basic rate set.

As described above, a TDF protocol can replace the conventional 802.11 DCF (distributed coordination function) or PCF (point coordination function) mechanism. Such a system can take advantage of a wide deployment of WLAN (802.11) network, and a WLAN chipset that may be getting more and more mature and cheap. This system provides a cost effective solution for bidirectional communication of CATV network by transmitting WLAN signals in cable network, even though the WLAN protocols are created for transmission/reception in an air environment rather than a cable network. In this system, the fundamental access method of TDF protocol is TDMA, which allows multiple users to share the same channel by dividing it into different time slots. The TDF stations transmit in rapid succession for uplink traffic, one after the other, each using their own time slot in a TDF superframe assigned by the TDF AP (access point) . For downlink traffic, the stations share the channels (as shown, for example, in the TDF superframe of Fig. 5), and select the frames targeting them by comparing the destination address information in the frames with their address.

Referring to Fig. 9, a typical TDF network 900 is shown. The network 900 provides a connection from user homes 910 and 920 to the Internet (or another resource or network) 930. The user homes 910 and 920 connect through an access point (AP) 940 over a cable system 950. The AP 940 may be located, for example, in a neighborhood of the homes 910 and 920, or in an apartment building that includes the homes (apartments, in this case) 910 and 920. The AP 940 may be owned by a cable operator, for example. The AP 940 is further coupled to a router 960 over an Ethernet network 970. The router 960 is also coupled to the Internet 930. As should be clear, the term "coupled" refers to both direct connections (no intervening components or units) and indirect connections (one or more intervening components and/or units) . Such connections may be, for example, wired or wireless, and permanent or transient.

The user homes 910 and 920 may have a variety of different configurations, and each home may be differently configured. As shown in the network 900, however, the user homes 910 and 920 each include a station (referred to as a modem) 912 and 922, respectively. The modems 912, 922 are coupled to a first host (hostl) 914, 924, and a second host (host2) 916, 926, over an Ethernet network 918, 928, respectively. Each host 914, 916, 924, and 926 may be, for example, a computer or other processing device or communication device. There are various ways in which the network 900 may allow multiple hosts (for example, 914, 916, 924, and 926) to connect to the router 960. Four implementations are discussed below, considering only the modem 912 and hosts 914 and 916, for simplicity. In a first method, the modem 912 acts as another router.

The hosts 914 and 916 are identified by their IP addresses, and the modem 912 routes IP packets from the hosts 914 and 916 to the router 960. This method 1 typically requires the modem 912 to run router software, which requires additional memory and increased processing power.

In a second method, the modem 912 acts as a bridge. The modem 912 and the AP 940 use the standard wireless distribution system (WDS) mechanism to convey layer 2 packets to the router 960. The hosts 914 and 916 are identified by their media access control (MAC) addresses. This method 2 is part of the 802.11 standard and can serve multiple hosts simultaneously. However, not all APs and modems support WDS, and those that do support WDS often have only limited support. For example, with some APs and modems, you cannot use Wi-Fi protected access (WPA) with WDS, and this may introduce security problems.

In a third method, the modem 912 uses MAC masquerade to change the source MAC address of Ethernet packets (the source being one of the hosts 914 and 916) to its own MAC address. So from the point of view of the router 960, the router 960 only sees the modem 912. The modem 912 can only serve one host at one time with this method. In a further method, the modem 912 uses encapsulation, as described in further detail below. Each of the above methods has advantages and disadvantages, and these advantages and disadvantages may vary depending on the implementation. However, the encapsulation method provides particular advantages in that it generally allows the modem to be simpler by not requiring that the modem run router software, it does not typically introduce security problems, and it can serve multiple hosts at one time.

Additionally, the encapsulation method avoids the large overhead associated with the first three methods, which transfer each packet from a host by using a single WLAN packet. Thus, the first three methods incur the overhead of the WLAN packet for every packet transferred from a host, and the throughput is correspondingly reduced. Such inefficiency is typically aggravated in the TDF environment. In the TDF environment, the duration of the time slot is fixed, and the time slot is designed to allow only one WLAN packet to transmit in one slot. Thus, only one host packet can be transmitted in each time slot. Accordingly, the encapsulation method generally provides one or more of a variety of advantages. Such advantages include, for example, simpler router design and operation, increased security, serving multiple hosts, and increased efficiency and throughput.

In summary, at least one implementation of the encapsulation method includes encapsulating multiple Ethernet packets into .one WLAN packet. The WLAN packet will be as big as the maximum length allowed by the TDF time slot. The AP

(for example, another modem) will decapsulate the WLAN packet into individual Ethernet packets and send them to the Router.

For communication in the reverse direction, a modem will decapsulate a WLAN packet and send the individual Ethernet packets to the host(s).

Referring to Fig. 10, an illustration 1000 includes multiple modems, two of which are explicitly shown, and an AP.

The illustration includes a modem #1 1010, a modem #N 1020, and an AP 1030, with each of the modems 1010 and 1020 coupled to the AP 1030 over a cable network 1040. Other implementations use separate cable networks for each of the modems.

The modems 1010 and 1020, and the AP 1030 include functional components of the same name, although some of the external connections are different and the components themselves perform different functions for a modem and for an

AP. Thus, a common unit is provided that serves as both a modem and an AP. However, it should be clear that different units could be designed for a modem and for an AP, with the different units performing only those functions required of a modem or an AP, respectively.

The modem 1010 includes a local applications layer 1011, followed by a TCP/IP layer 1012, followed by a bridge 1014.

The bridge 1014 is coupled to an Ethernet interface 1015, a packet aggregation/deaggregation module (PADM) 1016, and a WLAN interface 1017. The PADM 1016 is also coupled to the WLAN interface 1017. The Ethernet interface 1015 is coupled to an Ethernet network 1052, that is coupled to a first host (hostl) 1054 and a second host (host2) 1056.

The modem 1020 is analogous to the modem 1010. However, the modem 1020 is coupled to an Ethernet network 1062, and the Ethernet network 1062 is coupled to a first host (hostl) 1064 and a second host (host2) 1066. The components of the modem 1020 are shown as being identical to those of the modem 1010. However, it should be clear that various configuration parameters, for example, will be different when the modems 1010 and 1020 are set up and operational.

The AP 1030 includes a local applications layer 1071, followed by a TCP/IP layer 1072, followed by a bridge 1074. The bridge 1074 is coupled to an Ethernet interface 1077, a PADM 1076, and a WLAN interface 1075. The PADM 1076 is also coupled to the WLAN interface 1075. The Ethernet interface 1077 is coupled to an Ethernet network 1082, which in turn is coupled to a router 1090. The WLAN interfaces 1017 and 1075 are communicatively coupled to each other over the cable network 1040. The router 1090 is further coupled to the Internet 1095. Thus, a connection exists between the hosts 1054, 1056, 1064, 1066, and the Internet 1095.

The various local application layers (1011, 1071) are standard layers for running local applications and interfacing with other layers in the architecture. The various TCP/IP layers (1012, 1072) are standard layers for running TCP/IP and for providing the services typically provided by such layers, including interfacing to other layers in the architecture. The various Ethernet interfaces (1015, 1077) are standard units for interfacing to/from an Ethernet network. Such interfaces 1015, 1077 transmit and receive Ethernet packets and operate according to the Ethernet protocol. The various WLAN interfaces (1017, 1075) are units for interfacing to/from a WLAN network. Such interfaces 1017, 1075 transmit and receive WLAN packets and operate according to the WLAN protocol. However, the WLAN interfaces 1017, 1075 are actually coupled, in the illustration 1000, to a cable network 1040 rather than using wireless communication.

The Ethernet and WLAN interfaces 1015, 1017, 1075, and 1077 may be implemented, for example, in hardware such as a plug-in card for a computer. The interfaces may also largely be implemented in software such as a program that performs the functions of the interface using instructions that are implemented by a processing device. Such an interface will generally include a portion for receiving the actual signal (for example, a connector) and for buffering the received signal (for example, a transmit/receive buffer) , and typically a portion for processing the signal (for example, all or part of a signal processing chip) .

The various bridges (1014, 1074) are units that forward packets between an Ethernet interface and a WLAN interface. A bridge may be software or hardware implemented, or may only be a logical entity. Standard implementations for a bridge include a processing device (such as an integrated circuit) or a set of instructions running on a processing device (such as a processor running bridge software) . The PADMs 1016 and 1076 perform a variety of functions, including packet encapsulation and decapsulation, which are further described below. The PADMs 1016 and 1076 may be implemented in, for example, software, hardware, firmware, or some combination. Software implementations include, for example, a set of instructions such as a program for running on a processing device. Hardware implementations include, for example, a dedicated chip such as an application specific IC (ASIC) .

Most of the existing Cable networks are cable based bidirectional time division duplex (TDD) systems and utilize bi- directional amplifiers. These amplifiers however, have several limitations. First, the uplink and downlink power levels cannot be the same or nearly the same. Second, the two way loop has the potential to oscillate in bad isolation situations Third, they cannot be used in the newly developed cable networks, due to the problems encountered when attempting to by-pass CATV trunk amplifiers when applying MOCA or other DOCA protocols (e.g., advanced data over coax - ADOC) to existing cable networks .

The use of a bi-directional power amplifier of the present principles is one possible solution for implementation in CABLE based system with TDD mode like MOCA and other DOCA systems. The bi-directional amplifier of the present principles can solve the above-mentioned problems by providing the following advantages over known implementations: 1) equal power bi- directional amplification; 2) reduced oscillation; 3) suitable for newly developed cable networks; 4) simple detection; and 5) fast response with no malfunction operation.

As will be described in further detail below, an implementation of the bi-directional amplifier of the present principles can be implemented in an existing cable system anywhere, particularly between the Access point (AP) and the user modem.

Figure 11 shows an exemplary high level system diagram 1100 where the bi-directional amplifier of the present principles may be implemented. The system 1100 has many elements and can include a Core layer 1102 and a Pool Floor 1108, to which all other networks and services are connected. The core layer is generally made up of switches 1104 and a controller 1106 (e.g., a broadband remove access server - BRAS) . Examples of services or networks in communication with the core layer include a voice gateway 1114, an IPTV/VOD 1116, the internet 1118 and a DOCA network management system 1120. Those of skill in the art will recognize that various other services and/or networks may also be connected to the core layer 1102.

The Pool Floor 1108 is in communication with the core layer 1102 and is essentially the Access Point (AP) for all modem networks connected to the same, either through the EPON online terminal (OLT) 1110 or Access Switch 1112. An optical switch 1122 or other type of router connects the access point 1108 to one or more smaller networks of cable connected user modems 1126a. When using a DOCA network management system 1120 (or any other MOCA type system) to send data over the cable network to which the modems 26a are connected, a DOCA protocol (DOCAP) 1124 is carried on the cable.

The EPON OLT 1110 which is connected to a disperser 1128, which "disperses" the connection to one or more optical network units (ONUs) 1130 The ONU' s then distribute the signals to one or more modems 1126b in a cable connected network of modems. The bi-directional amplifier of the present principles can be positioned, for example, anywhere between the Access point 1112 and the modems 1126a or the EPON OLT 1110 and the modems 1126b. The internal components of the core layer 1102 (e.g., the core switches 1104 and the broadband remote access server 1106 are interconnected by fiber optic lines 1131, while the gateway 1114, IPTC/VOD 1116, Internet 1118 and DOCA network management system 1120 are generally connected to the core layer 1102 by coaxial cables 1132. The core layer 1102 is connected to the pool floor also by fiber optic lines 1131

The OLT 1110 and the access switch (access point) 1112 can be connected to the disperser 1128 and optical switch (router) 1122 using fiber lines 1131 as well. The disperser 1128 can be connected to the ONUs 1130 using fiber lines 1131. The ONUs 1130 and optical switch (routers) 1122 are connected to the DOCAPs 1124 via Ethernet cables 1134, and the modems 1126 are connected to the DOCAPs 1124 via coaxial cables 1132.

Figure 12 shows a block diagram of the bi-directional amplifier 1200 according to an implementation of the present principles. The bi-directional amplifier 1200 is coupled between the AP and a modem and includes a directional coupler 1202, a power detector 1204 connected to the directional coupler, a voltage division network 1206 in communication with one side of the power detector, and a voltage comparator 1208. The voltage comparator 1208 receives signals from the power detector and is connected to a single pole double throw (SPDT) switch 1210. An amplifier with bypass mode 1212 is connected to the directional coupler 1202 and the SPDT switch 1210.

A bi-directional power detector unit may be formed, for example, from the power detector 1204, from the directional coupler 1202 combined with the power detector 1204., or from other combinations of elements including the voltage division network 1206, the voltage comparator 1208, and/or the switch 1210. A bi-directional power amplifier unit may be formed, for example, from the amplifier 1212 alone or in combination with one or more other elements from Figure 12.

Figure 13 is a schematic representation of an implementation of the bi-directional amplifier 1200 according to an implementation of the present principles .

The operation of the bi-directional amplifier 1200 is now described with reference to figures 12 and 13. It is understood that other schematic implementations of the amplifier 1200 are possible and envisioned. Further, the following operation is particular to the schematic implementation illustrated in Figure 13, but one of ordinary skill will recognize that the operation can be modified to accommodate other schematic implementations. Continuing with the operation, the Amplifier 1212 includes a bypass function, such that when it is in an amplification state, it can provide +15dB gain, and when in bypass mode, it can provide a -2dB insertion loss. The operation status of the amplifier 1212 is under the control of the SPDT switch 1210. The bi-amplifier with bypass mode 1212 is the core of the amplifier 1200. When in amplification mode, amplifier 1212 can provide >15dB gain, and when it is in bypass mode, it can provide -2dB insertion loss. These two states can be switched by the switch 1210 and/or by additional external components. As can be seen from the example of Figure 13, at each state (transmit or receive) , two amplifiers 1213 will be in amplification state and the other two are in bypass mode.

The directional coupler 1202 is a high performance directional coupler that can provide single way power detection (contrary to known commercial two-way couplers) . The coupler 1202 includes two directional couplers 1302a and 1302b configured to detect transmit (uplink) power and receive (downlink) power, respectively. The directional coupler 1202 can provide >25dB directivity with -IdB insertion loss and - 1OdB coupled loss, and 28dB directivity at IGHz.

The power detector 1204 is a high sensitivity power detector and includes RF power detectors 1304a, 1304b which can convert RF signals to DC voltage, where the DC voltage is maintained at a fixed ratio to the RF power. The higher the RF power, the higher the DC voltage at the output. The two converted DC voltages are input to the voltage comparator 1208. Commercially available RF power detectors can achieve, for example, -45dBm RF power detection sensitivity.

The voltage comparator 1208 has two inputs (inverting and non-inverting) and provides one of two output status indications based on the inputs received from the power detector 1204. For example, if the non-inverting input is larger than the inverting input, the comparator 1208 will output a high voltage level, and conversely, if the non- inverting input is lower than the inverting input, the comparator will output a low voltage level. The non-inverting input is pre-biased by a very low DC voltage (e.g., ~0.lV) provided by the voltage division network 1206. This pre- biasing prevents abnormal states of the comparator 1208 during signal input.

The output of the voltage comparator 1208 controls the output of the SPDT switch 1210 so that it can control the status of the amplifier 1200.

As will be appreciated by those of skill in the art, when there are no signals transmitted at both uplink and downlink, the bi-directional amplifier 1200 is in a "Receive" state (i.e., Modem to AP amplifier open, AP to Modem amplifier by-pass) as established by the pre-bias voltage provided by the voltage division network 1206 to the non-inverting input of the comparator 1208. When there is an uplink signal transmitted, the bi-directional amplifier will still remain in the "receive" state since the voltage comparator output will not change (or flip from high to low) .

When there is a downlink signal transmitted, the comparator 1208 will flip or change states due to an increase in voltage on the inverting input. This will cause the switch 1210 to switch the bi-directional amplifier to a "transmit" state. When the downlink signal transmission is completed, the voltage on the inverting input decreases to 0 (or substantially zero) and the comparator 1208 responds by flipping back and causing switch 1210 to switch the bi-directional amplifier back to the "receive" state.

As used herein, the equal power bi-directional amplification means the ability to obtain the same power output (-OdBm) and the same gain (~2β-30dB) in both directions. Those of skill in the art will recognize that maintaining the same power output bi-directional amplification is not easy to realize in TDD mode two way communication system due to the directivity (e.g., ~20) of the power detector.

In accordance with an aspect of the present principles, and in order to achieve equal power bi-directional amplification, the power detector 1204 is disposed on the Access Point (AP) side of the amplifier, and the low pre-bias voltage (e.g., ~0.1V) from the voltage division network 1206 is applied at the non-inverting input of the comparator 1208. Through this design, the same power amplification is achieved even when power detectors with poor directivity are used. The primary reason for this configuration of the directional couplers 1202, is that when placing the directional couplers on the AP side and modem side or just the modem side of the bi-directional amplifier, the system will typically not always work properly. There are three cases or scenarios that relate to the placement of the directional couplers 1202: 1) by placing the directional couplers on separate/opposite sides of the bi-directional amplifier, the amplifier signal leakage to the directional couplers can cause a malfunction; 2) both directional couplers are placed on the modem side of the bidirectional amplifier - According to WiFi protocol, the bi- directional amplifier should be in a receive state if there is no signal (i.e., uplink or downlink) at either side of the amplifier. When the directional couplers are on the modem side, if a downlink signal is transmitted, it cannot reach the directional couplers due to the isolation of the bi-directional amplifier. Therefore the bi-directional amplifier remains in the receive mode and the system will malfunction; and 3) by placing both directional couplers on the AP side, the system works as described by the present principles.

Leakage, as mentioned above, may occur in, for example, a system in which the couplers and/or detectors are on opposite sides of the amplifier. The leakage may occur due to the fact that when an uplink signal (i.e., Modem to AP) transmits, the signal detected from an AP side (forward) power detector will be larger than the signal detected from the Modem side (backward) detector because some of the amplified power leaks over into the AP-side power detector. This will cause the voltage comparator to switch to a transmit mode from a receive mode. An analogous result holds for a downlink signal.

Other implementations place the power detectors on the modem side of the amplifier, and/or pre-bias the inverting input . In accordance with another aspect, the present principles provides for reduced oscillation. This is due' to the fact that there is only one physical signal path, therefore no loop oscillating can occur. In addition, no external high selectivity Band Pass Filter (BPF) is required. As a result of the implementation of the present principles, there is no strict requirement for the directional coupler 1202. As such, commonly available directional couplers could be used in an implementation of the present principles. This is due to the fact that if we were to implement an AP side and Modem side directional coupler (power detector) , the subtraction of the AP side detector signal from the Modem side detector signal will determine the operational state of the switch 1210, and thus the state of the bi-directional amplifier 1212. By placing both directional couplers on the AP side of the bi-directional amplifier 1212, both the downlink and uplink signals will be almost the same power level when they pass through the directional coupler 1202. Therefore, even with directional couplers having poor directivity (e.g., 2OdB isolation) , the 2OdB margin can also guarantee the subtraction value will be proper and thus guaranteeing the operational state of the switch 1210. According to an implementation of the present principles, all the components provide nano-second level operating responses. Therefore the total delay time, is <300ns (e.g., directional coupler 1202 - <10ns, power detector 1204 - 85ns, voltage comparator 1208 - 40ns, SPDT 1210 - 12ns and power amplifier 1212 - 100ns) , which is less than the requirements for TDD mode communication systems which is generally several micro-seconds .

In terms of the potential for malfunctions, they can be divided into several cases: Case 1: When no signal input at both sides (i.e., no transmit or receive power) - the amplifier 1212 will be in receive state (i.e., the path from Modem to AP is open) ;

Case 2: When there is signal transmitted from AP to MODEM, the forward detected power (e.g., 0.2-0.5V) will be much larger than the backward detected power (<0.1V), so the voltage comparator 1208 will flip and the amplifier 1212 will switch to the transmit state (i.e., path from AP to MODEM); and

Case 3: When there is signal transmit from MODEM to AP, the backward detected power (e.g., 0.6-0.8V) will be much larger than the forward detected power (<0. IV) . Since there is the pre-biased resistive voltage (e.g., 0.1V) at the non- inverting input port of the power comparator 1208, the amplifier 1212 will remain in the "receive" state. Note that the backward detected power is detecting a signal that has already been amplified due to the fact that the amplifier is presumed to be in the receive state. Note also that in normal TDD operations, only one signal is present at a time—only the uplink or the downlink. Further, the amplifier will typically return to a receive state between such signals being present. However, if multiple signals are present at the same time, the Wifi protocol (CSMA/CD) typically avoids a conflict.

Thus, it will be clear to those of skill in the art that in the event of any of the above mentioned cases potential operational situations that may cause malfunction, the amplifier 1212 will transmit signals properly and no malfunction will occur.

In accordance with another implementation of the present principles, the bi-directional amplifier 1200 is suitable for use in newly developed cable-based communication networks. However, in this implementation, there is one obstacle in how to bypass the CATV trunk amplifier when newly developed technology such as MOCA or other data over coax systems (e.g., advanced data over coax (ADOC) ) is applied to current ready CATV feedline network.

The bi-directional amplifier 1212 of the present principals can be easily placed in parallel with CATV trunk amplifier with minimum insertion loss (e.g.., <ldB) brought to the TV signal. Figure 14 shows an exemplary implementation 1400 of the bi-directional amplifier 1212 in parallel with the CATV trunk amplifier 1410. The power splitter 1406 receives the TV signal 1404 and the DOCA signal 1402 with DOCAP 1124 and outputs various cable distributions 1408a-1408d. Each cable distribution 1408 will, at some point, have a CATV trunk amplifier 1410. For exemplary purposes, the cable distribution 1408d is shown having the CATV trunk amplifier 1410.

In this configuration, the bi-directional amplifier 1212 provides suitable gain compensation (e.g., 26-3OdB) to the bi- directional ADOC signal that is the same (or substantially the same) as CATV trunk amplifier compensation to TV signal (e.g., 26dB) . The gain compensations may compensate for, e.g., path loss. Those of skill in the art will recognize that filters (e.g., a band splitter) are used in order to separate the TV signal from the ADOC signal. As such, in one implementation the filter or filters would be disposed at the inputs and outputs of the CATV trunk amplifier 1410 and bi-directional amplifier 1212. In this mode, the amplifier can be used for TDD mode and will comply with current WiFi and WiMax systems, especially for cable based MOCA systems .

Figure 15 shows a method 1500 according to an implementation of the present principles. Initially, the presence of an uplink or downlink signal is monitored (1502). When a downlink signal only is detected, the bi-directional amplifier within the bi- directional amplifier circuit is switched from a receive state to a transmit state (1504) . The method further includes (as shown in Figure 16) the steps of maintaining the bi-directional amplifier in a receive state when only an uplink signal is detected (1506) and neither an uplink nor downlink signal is detected (1508) . As discussed above, the maintaining of the receive state is performed by applying a pre-bias voltage to the non-inverting input of the voltage comparator 1208 within the bidirectional amplifier circuit 1200.

The implementations described herein may be implemented in, for example, a method or process, an apparatus, or a software program. Even if only discussed in the context of a single form of implementation (for example, discussed only as a method) , the implementation of features discussed may also be implemented in other forms (for example, an apparatus or program) . An apparatus may be implemented in, for example, appropriate hardware, software, and firmware. The methods may be implemented in, for example, an apparatus such as, for example, a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device. Processing devices also include communication devices, such as, for example, computers, cell phones, portable/personal digital assistants ("PDAs"), and other devices that facilitate communication of information between end-users.

Implementations of the various processes and features described herein may be embodied in a variety of different equipment or applications, particularly, for example, equipment or applications associated with data transmission and reception. Examples of equipment include video coders, video decoders, video codecs, web servers, set-top boxes, laptops, personal computers, and other communication devices. As should be clear, the equipment may be mobile and even installed in a mobile vehicle .

Additionally, the methods may be implemented by instructions being performed by a processor, and such instructions may be stored on a processor-readable medium such as, for example, an integrated circuit, a software carrier or other storage device such as, for example, a hard disk, a compact diskette, a random access memory ("RAM") , or a readonly memory ("ROM") . The instructions may form an application program tangibly embodied on a processor-readable medium. As should be clear, a processor may include a processor-readable medium having, for example, instructions for carrying out a process . As should be evident to one of skill in the art, implementations may also produce a signal formatted to carry information that may be, for example, stored or transmitted. The information may include, for example, instructions for performing a method, or data produced by one of the described implementations. Such a signal may be formatted, for example, as an electromagnetic wave (for example, using a radio frequency portion of spectrum) or as a baseband signal. The formatting may include, for example, encoding a data stream, packetizing the encoded stream, and modulating a carrier with the packetized stream. The information that the signal carries may be, for example, analog or digital information. The signal may be transmitted over a variety of different wired or wireless links, as is known. A number of implementations have been described.

Nevertheless, it will be understood that various modifications may be made. For example, elements of different implementations may be combined, supplemented, modified, or removed to produce other implementations. Additionally, one of ordinary skill will understand that other structures and processes may be substituted for those disclosed and the resulting implementations will perform at least substantially the same function (s), in at least substantially the same way(s), to achieve at least substantially the same result (s) as the implementations disclosed. Accordingly, these and other implementations are contemplated by this application and are within the scope of the following claims.

Claims

CLAIMSWhat is claimed is :

1 . An apparatus comprising : a bi-directional power amplifier unit (1212) configured to amplify signals having a first direction and to amplify signals having a direction opposite the first direction; and a bi-directional power detector unit (1202-1204) coupled to the bi-directional power amplifier unit so as (1) to detect power in a signal having the first direction before the signal having the first direction is amplified by the bi-directional power amplifier unit, and (2) to detect power in a signal having the opposite direction after the signal having the opposite direction is amplified by the bi-directional power amplifier unit.

2. The apparatus of claim 1 wherein the bi-directional power detector unit is coupled to the power amplifier unit over a communication path configured to carry amplified signals having the opposite direction and non-amplified signals having the first direction.

3. The apparatus of claim 1, wherein said bi-directional power detector unit is connected to an access point side of the bidirectional power amplifier.

4. The amplifier circuit of claim 1, further comprising: a switch in communication with the bi-directional power amplifier unit for switching the bi-directional power amplifier unit between a receive state and a transmit state; and a voltage comparator having an inverting input and a non- inverting input connected to outputs of said bi-directional power detector unit, and an output connected to said switch.

5. The amplifier circuit of claim 4, further comprising a bias voltage circuit configured to provide a pre-bias voltage to the non-inverting input of the voltage comparator.

6. The amplifier circuit of claim 1, wherein said bidirectional power detector unit comprises a first directional coupler configured to detect transmit (uplink) power and a second directional coupler configured to detect receive (downlink) power,

7. The amplifier circuit of claim 6, wherein said bidirectional power detector unit further comprises a first RF power detector and a second RF power detector, each configured to convert RF power to DC voltage .

8. The amplifier circuit of claim 4, wherein said voltage comparator causes said switch to maintain said bi-directional power amplifier in a receive state when no transmit (uplink) power and no receive (downlink) power is detected.

9. The amplifier circuit of claim 4, wherein said voltage comparator causes said switch to maintain said bi-directional power amplifier in a receive state when a transmit (uplink) power signal is detected.

10. The amplifier circuit of claim 4, wherein said voltage comparator causes said switch to flip the bi-directional power amplifier unit to a transmit state when a receive (downlink) power signal is detected.

11. An amplifier circuit comprising: a directional coupler (1202) having an input and an output; a bi-directional power amplifier (1212) having a by-pass mode and having an input coupled to the output of the directional coupler and an output configured to be connected to a modem, wherein the input of the directional coupler is configured to be connected to and Access point, and said directional coupler is connected on the Access point side of said bi-directional power amplifier; a power detector (1204) connected to the directional coupler and configured to detect uplink and downlink power; a voltage comparator (1208) having an inverting and non- inverting input, each connected to the power detector; a voltage division network (1206) connected to the non- inverting input of said voltage comparator and configured to provide a pre-bias voltage to the voltage comparator; and a switch (1210) connected to the voltage comparator and the bi-directional amplifier, said switch configured to change an operation state of the bi-directional power amplifier in response to signals received from the voltage comparator.

12. The amplifier circuit of claim 11, wherein the directional coupler further comprises two directional couplers, one configured to detect an uplink signal and one configured to detect a downlink signal.

13. The amplifier circuit of claim 11, wherein the power detector comprises two RF power detectors, said RF power detectors configured to convert RF signals to DC voltage.

14. The amplifier circuit of claim 11, wherein said switch comprises a single pole double throw switch configured to switch the bi-directional amplifier between an active mode and a by-pass mode in response to detected uplink and/or downlink signals.

15. The amplifier circuit of claim 11, wherein the directional coupler, the bi-directional amplifier, the power detector, the voltage comparator and the switch all comprise high speed operating responses such that a total operating response time of the amplifier circuit is <300ns.

16. A method comprising: monitoring the presence of an uplink or downlink signal at an access point side of a bi-directional amplifier within a bidirectional amplifier circuit; and switching the bi-directional amplifier to a transmit state when only a downlink signal is present.

17. The method of claim 16, further comprising: maintaining the bi-directional amplifier within the bidirectional amplifier circuit in a receive state when an uplink signal is present; and maintaining the bi-directional amplifier within the bidirectional amplifier circuit in a receive state when no uplink or downlink signal is present.

18. The method of claim 16, wherein said monitoring is performed by a directional coupler positioned on the access point side of the amplifier.

19. The method of claim 17, wherein said steps of maintaining further comprise applying a pre-bias voltage to a non-inverting input of a voltage comparator within the bi-directional amplifier circuit .

20. An apparatus comprising: means for monitoring (1202-1204) the presence of an uplink or downlink signal at an access point side of a bi-directional amplifier within a bi-directional amplifier circuit; and means for switching (1210) the bi-directional amplifier to a transmit state when only a downlink signal is present.

21. The apparatus of claim 20, further comprising: means for maintaining (1208) the bi-directional amplifier within the bi-directional amplifier circuit in a receive state when an uplink signal is present; and further means for maintaining (1206) the bi-directional amplifier within the bi-directional amplifier circuit in a receive state when no uplink or downlink signal is present.

22. The apparatus of claim 21, wherein said further means for maintaining further comprises means for applying a pre-bias voltage to a non-inverting input of a voltage comparator connected to a switch that controls the operation mode of the bidirectional amplifier within the bi-directional amplifier circuit

23. An amplifier circuit for use with existing CATV systems, where the CATV systems include one or more cable distributions, each cable distribution having at least one CATV trunk amplifier, the amplifier circuit comprising: a bi-directional amplifier unit (1212) arranged in parallel with each CATV trunk amplifier on a cable distribution, said bidirectional amplifier unit enabling the passage of data over coaxial (DOCA) protocols to operate on the CATV system without interfering with or causing losses to a TV signal carried on the CATV cable distributions.

24. A cable system comprising: at least one power splitter (1406) having at least one input connected to a CATV cable based television service provider and at least one input connected to a data over coaxial cable (DOCA) protocol system, said power splitter having at least one cable distribution output; a CATV trunk amplifier (1410) connected in series with the at least one cable distribution; and a bi-directional amplifier circuit (1212) connected in parallel to said at least one cable distribution around said CATV trunk amplifier.

25. The cable system of claim 24, wherein said bi-directional amplifier circuit comprises: a directional coupler having an input and an output, said directional coupler configured to detect the presence of an uplink or downlink signal transmit; a bi-directional amplifier connected to the detector; and a switch in communication with the detector and bidirectional amplifier for switching the bi-directional amplifier between a receive and a transmit state; wherein said directional coupler is connected to an access point side of the bi-directional amplifier.

26. The amplifier circuit of claim 25, further comprising: a power detector connected to said directional coupler; and a voltage comparator having an inverting input and a non- inverting input connected to outputs of said power detector, and an output connected to said switch.

27. A method comprising: detecting a signal, having a particular transmission direction, at a first side of a power amplifier; amplifying the detected signal having the particular transmission direction using the power amplifier; detecting a signal, having a transmission direction opposite the particular transmission direction, at the first side of the power amplifier; and amplifying the detected signal having the opposite transmission direction using the power amplifier.