# Patent

## Title
Modular wireless communications platform

## Abstract

A modular wireless communications platform is provided. The modular wireless communications platform has a modular host unit and a modular remote unit in communication with the modular host unit. The modular host unit has a serial radio frequency communicator configured to convert serial digital data into RF sampled data and configured to convert RF sampled data into serial digital data. The modular host unit also has an interface coupled to the serial radio frequency communicator and configured to allow transfer of the RF sampled data from the serial radio frequency communicator to a digital to analog radio frequency transceiver module. Likewise, the modular remote unit has a serial radio frequency communicator configured to convert serial digital data into RF sampled data and configured to convert RF sampled data into serial digital data. The modular remote unit also has an interface coupled to the serial radio frequency communicator and configured to allow transfer of the RF sampled data from the serial radio frequency communicator to a digital to analog radio frequency transceiver module.

## Background
RELATED APPLICATIONS
This application is related to the following commonly assigned applications filed on even date herewith, each of which is hereby incorporated herein by reference:
U.S. patent application Ser. No. 11/627,255, entitled “DISTRIBUTED REMOTE BASE STATION SYSTEM” (the '829 Application).
BACKGROUND
Technology is continually evolving as consumer needs change and new ideas are developed. Nowhere is this more apparent than in the wireless communications industry. Wireless communication technologies have changed drastically over the recent past and have affected many aspects of our daily lives. As new wireless technologies are developed, companies must invest large amounts of time and resources to upgrade all their existing hardware so that it is compatible with the new technology. Often a change in one component of a system requires an update of the entire system.
The infrastructure of a wireless communication system is commonly designed for a specific technology and a specific frequency band. Thus, once a service provider installs a particular infrastructure, a complete overhaul of a system is required to upgrade to a new technology or change to another frequency band. In addition, if a service provider would like to carry multiple frequency bands, the provider generally has to install a different set of hardware for each technology and frequency band carried. Thus, if the service provider carries four frequency bands of service for mobile customers; four different sets of hardware must be installed in each transmission and reception location.
In addition to changes in technology, consumer demand for a particular service may change after a service is installed. For example, access points initially deployed using over-the-air repeaters or simulcast distributed antenna systems, may need to be replaced with full base stations to support the increased consumer demand. This again, will require major overhauls of existing infrastructure. Moreover, these changes occur not infrequently, are costly and are often necessary to keep pace with competitors within the industry.
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 a wireless communications platform that keeps pace with the rapid changes in wireless communications protocols.
SUMMARY
The above-mentioned problems of current systems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification. The following summary is made by way of example and not by way of limitation. It is merely provided to aid the reader in understanding some of the aspects of the invention. In one embodiment, a modular wireless communications platform is provided. The modular wireless communications platform has a modular host unit and a modular remote unit in communication with the modular host unit. The modular host unit has a serial radio frequency communicator configured to convert serial digital data into RF sampled data and configured to convert RF sampled data into serial digital data. The modular host unit also has an interface coupled to the serial radio frequency communicator and configured to allow transfer of the RF sampled data from the serial radio frequency communicator to a digital to analog radio frequency transceiver module. Likewise, the modular remote unit has a serial radio frequency communicator configured to convert serial digital data into RF sampled data and configured to convert RF sampled data into serial digital data. The modular remote unit also has an interface coupled to the serial radio frequency communicator and configured to allow transfer of the RF sampled data from the serial radio frequency communicator to a digital to analog radio frequency transceiver module.



BRIEF DESCRIPTION OF THE DRAWINGS
The present invention can be more easily understood and further advantages and uses thereof more readily apparent, when considered in view of the detailed description and the following figures in which:
FIG. 1 is an illustration of one embodiment of a system using a modular wireless communications platform;
FIG. 2 illustrates a schematic view of one embodiment of a host unit for use in the system of FIG. 1;
FIG. 3 illustrates a schematic view of one embodiment of a remote unit for use in the system of FIG. 1;
FIG. 4 illustrates a schematic view of one embodiment of a digital to analog radio frequency transceiver module for use in either the host unit of FIG. 2 or the remote unit of FIG. 3;
FIG. 5 illustrates a schematic view of one embodiment of a serial radio frequency communicator for use in either the host unit of FIG. 2 or the remote unit of FIG. 3;
FIG. 6 illustrates another configuration of the system of FIG. 1;
FIG. 7 illustrates yet another configuration of the system of FIG. 1;
FIG. 8 illustrates one embodiment of a distributed base station system; and
FIG. 9 illustrates another embodiment of a distributed base station system.



In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the present invention. Reference characters denote like elements throughout Figures and text.
DETAILED DESCRIPTION
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments in which the device may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense.
The present apparatus is a modular wireless platform that enables a system facilitator to easily and inexpensively adapt their wireless system for use with different data transport mechanisms, frequency bands, communication technologies, and intelligence distribution. This modular platform is made up of a reconfigurable host unit and a reconfigurable remote unit designed for use in a system with a central node and a plurality of distributed antennas. The host unit is located near the central node and facilitates transmission/reception of information to/from the remote units which are located remotely with an accompanying antenna. The remote units function to transmit/receive transmissions from the host unit and transmit/receive wireless signals over accompanying antenna to mobile costumers.
Host unit and remote unit have a modular design and defined interfaces that allow components to be removed and installed to adapt to the needs of the service providers. Both host and remote unit are designed around a serial radio frequency (SeRF) communicator and have a defined interface where different varieties of digital to analog radio frequency transceiver (DART) modules can be connected and disconnected. There are many different DART modules, and each DART module is designed for a particular technology and frequency band. Thus, technology and frequency band adjustments can be made by simply replacing the DART module in the host unit or remote unit. Additionally, host unit and remote unit are designed to allow different transport mechanisms between the host unit and remote unit. For example, the same host unit and remote unit that use fiber optic for inter-unit transmission can be adapted to use E Band wireless transmission instead of or concurrently with the fiber optic. Finally, wireless processing functionality can be placed all on a base station near the central node, or the functionality can be distributed throughout each of the remote units. The flexibility to modify the functionality of each remote unit allows the wireless platform to support centralized base stations and distributed base stations, either separately or concurrently.
FIG. 1 is a block diagram of one embodiment of a system 100 using a modular wireless communications platform. System 100 is a field configurable distributed antenna system (DAS) that provides bidirectional transport of a fixed portion of RF spectrum from an Internet Protocol (IP) gateway 101 to a remote antenna 108. Along with IP gateway 101 and remote antenna 108, system 100 includes a base station 103, a host unit 102, a transport mechanism 104, and a remote unit 106. Host unit 102, a modular host transceiver and remote unit 106, a modular remote radio head, work together to transmit and receive data to/from remote antennas. In this embodiment, host unit 102 provides the interface between a base station 101 a signal transport mechanism 104. Remote unit 106 provides the interface between transport mechanism 104 and a remote antenna 108. In this embodiment, signal transport mechanism 104 is an optical fiber, and host unit 102 sends optical signals through the optical fiber to remote unit 106.
In the transmission direction of transport, base station 103 performs baseband processing on IP data from IP gateway and places the IP data onto a channel. In one embodiment base station 103 is an IEEE 802.16 compliant base station. Optionally, base station 103 may also meet the requirements of WiMax, WiBro, or a similar consortium. In another embodiment, base station 103 is an 800 MHz or 1900 MHz base station. In yet another embodiment, the system is a cellular/PCS system and base station 103 communicates with a base station controller. In still another embodiment, base station 103 communicates with a voice/PSTN gateway. Base station 103 also creates the protocol and modulation type for the channel. Base station 103 then converts the IP packetized data into an analog RF signal for transmission over antenna 108. Base station 103 sends the RF signal to host unit 102. Host unit 102 converts the RF signal for long distance high speed transmission over transport mechanism 104. Host unit 102 sends the signal over transport mechanism 104, and the signal is received by remote unit 106. Remote unit 106 converts the received signal back into an RF signal and transmits the signal over antenna 108 to consumer mobile devices.
FIG. 2 illustrates a schematic diagram of one embodiment of a host unit 102 for use in a modular wireless communications platform. Host unit 102 has a serial radio frequency (SeRF) communicator 202 that is coupled to a digital to analog radio frequency transceiver (DART) interface 204. DART interface 204 has a plurality of DART connectors each of which is configured to receive a pluggable DART module 208. Further, DART connectors are configured to connect DART module 208 to SeRF communicator 202. DART interface 204 is a common interface that is configured to allow communication between SeRF communicator 202 and different varieties of DART modules 208. Additionally, DART interface 204 allows multiple DART modules 208, 210, 212 to connect to a single SeRF communicator 202. In this embodiment, DART interface 204 is a passive host backplane to which SeRF communicator 202 also connects. In this embodiment, DART interface 204 has eight DART connectors for a DART module 208. In another embodiment, instead of being a host backplane, DART interface 204 is integrated with SeRF communicator 202.
DART modules 208, 210, 212 provide bi-directional conversion to/from analog RF signals from/to digital sampled RF. In one direction of communication, DART module 208 receives an incoming analog RF signal from base station 103 and converts the analog signal to a digital signal for use by SeRF communicator 202. In the other direction DART modules 208, 210, 212 receive digital sampled RF data from SeRF communicator 202 and convert the data to analog RF for use by base station 103.
Each DART module 208, 210, 212 has a common communication interface for communication with SeRF communicator 202, and a RF processing portion that is exclusive to one frequency band and communication technology. Each DART module 208, 210, 212, therefore, converts to/from one analog RF to the digital signal used by SeRF communicator. For example, DART module 208 is designed to transmit 850 MHz cellular transmissions. As another example, DART module 210 transmits 1900 MHz PCS signals. Some of the other options for DART modules 208, 210, 212 include Nextel 800 band, Nextel 900 band, PCS full band, PCS half band, BRS, WiMax, and the European GSM 900, DCS 1800, and UMTS 2100. By allowing different varieties of DART modules 208, 210, 212 to be plugged into DART interface 206, host unit 102 is configurable to any of the above frequency bands and technologies as well as any new technologies or frequency bands that are developed. Host unit 102, once installed, is field configurable to transmit a variety desired by insertion of a different DART module. Additionally, since SeRF communicator 202 is configured to communicate with multiple different DART modules 208, 210, 212, a single host unit 102 can transmit/receive multiple frequency bands or technologies.
SeRF communicator 202 provides bi-directional conversion to/from a SeRF stream from/to a high speed optical serial data stream. In one direction, SeRF communicator 202 receives incoming SeRF streams from DART modules 208, 210, 212 and sends a serial optical data stream over transport mechanism 104 to remote unit 106. In the other direction, SeRF communicator 202 receives an optical serial data stream from a remote unit 106 and provides SeRF streams to DART modules 208, 210, 212. In one embodiment, the SeRF stream between DART module 208 and SeRF communicator is a parallel stream. In another embodiment, SeRF stream is a serial data stream.
SeRF communicator 202 also allows multiple DART modules 208, 210, 212 to operate in parallel. SeRF communicator 202 actively multiplexes the signals from each DART module 208, 210, 212 such that they are sent simultaneously over a single transport mechanism 104. To accomplish this, SeRF communicator 202 presents a clock signal to each DART module 208, 210, 212 to ensure synchronization.
In one embodiment, an optical multiplex module 214 is optically coupled to SeRF communicator 202. Optical multiplex module 214 performs multiplexing/de-multiplexing of an optical serial data stream to/from SeRF communicator 202 over transport mechanism 104. In this embodiment, optical multiplex module 214 performs wavelength division multiplexing.
In another embodiment, transport mechanism 104 is a wireless millimeter wave signal transceiver (e.g. E Band/70 GHz radio). In this embodiment, host unit 102 sends optical signals to the millimeter wave transceiver which converts the optical signals into millimeter waves and transmits the millimeter waves to a similar millimeter wave transceiver connected to remote unit 106. In yet another embodiment, transport mechanism 104 is a microwave radio transceiver. In still another embodiment, transport mechanism 104 is a T1 connection for transmission of IP data.
FIG. 3 is a schematic diagram of one embodiment of a remote unit 106 for use in a modular wireless communications platform. Remote unit 106 has a SeRF communicator 302, a SeRF interface 304, at least one DART interface 306. In this embodiment, DART modules 308, 309, 311, power amplified 310, duplexer/linear amplifier 312, and optical multiplex module 314 are all installed in remote unit 106 which is connected to antenna 108.
SeRF communicator 302 is designed and performs similar to SeRF communicator 202 of host unit 102. Likewise, DART modules 308, 309, 311 have the same features and design options as DART modules 208, 210, 212 of host unit 102. There is a slight difference from host unit 102, however, in the manner in which SeRF communicator 302 and DART modules 308, 309, 311 are connected. In this embodiment of remote unit 106, SeRF communicator 302 has a SeRF interface 304 which is used to link SeRF communicator to SeRF cables 305. SeRF cables 305 are used to allow DART modules 308, 309, 311 to be physically spaced from SeRF communicator 302 and from other DART modules. SeRF cables 305 connect to DART interface 306. DART modules 308 connected to DART interface 306 and communicate with SeRF communicator 302 through DART interface 306 over SeRF cables 305 and through SeRF interface 304. In another embodiment, SeRF interface 304, and SeRF cables 305 are eliminated and DART interface 306 is integrated into SeRF communicator 302.
DART modules 308 perform similar to DART module 208, except the ultimate destination/origination of the signals to/from DART modules 308 is antenna 108 and not base station 101 as in host unit 102. Optical multiplex module 314 also performs similarly to optical multiplex module 214 of host unit 102.
In the transmission direction, once a signal is converted to analog RF by DART module 308, the signal is sent through RF interface 322 (explained below) to power amplifier 310. Power amplifier 310 amplifies the RF signal received from DART module 308 for output through duplexer/linear amplifier 312 to antenna 108. Similar to DART modules 308, 309, 311, power amplifier 310 is designed for a certain frequency band and technology. Power amplifier 310 is, therefore, removable and is plugged into a power amplifier connector on remote unit 106 which is configured to receive power amplifier 310. Power amplifier connector is configured to couple power amplifier to duplexer/linear amplifier 312 and to DART module 308. Power amplifier 310 also has an alarm and control line that is connected to DART interface 306 for communication to SeRF communicator 302.
Once the signal is amplified by power amplifier 310, duplexer/linear amplifier 312 provides duplexing of the signal which is necessary to connect transmit and receive signals to a common antenna. Duplexer/linear amplifier 312 also provides low noise amplification of received signals and rms power detection of incident and reflected RF power in transmission signal. Similar to DART modules 308, 309, 311 and power amplifier 310, duplexer/linear amplifier 312 is frequency band and technology specific, and is removable. Duplexer/linear amplifier 312 plugs into a connector in remote unit 106 configured to receive duplexer/linear amplifier 312. Furthermore, the connector is configured to couple duplexer/linear amplifier 312 to power amplifier 310 and to antenna 108. Duplexer/linear amplifier 312 also has a control and alarm line that is connected to DART interface 320 for communication to SeRF communicator 302. In this embodiment, the frequency band and technology allow use of a single power amplifier 310 and duplexer/linear amplifier 318 by both DART module 308 and DART module 309. In this embodiment, a RF interface 322 is placed between power amplifier 310, duplexer/linear amplifier 312 and DART modules 308, 309. RF interface 322 provides RF splitting/combining of the RF transmit and receive signals necessary to allow connection of two DART modules 308, 309 to a single power amplifier 310 and duplexer/linear amplifier 312.
FIG. 4 shows a schematic view of one embodiment of a DART module 400 for use in either host unit 102 or remote unit 106. There are multiple embodiments of DART module 400 as described above, however, the common elements are described hereafter. DART module 400 has an edge connector 402 for connection to a DART interface. DART module 400 has two main signal paths; a transmission path 404 and a reception path 406. For signals received from a SeRF communicator, DART module 400 forms parallel digital RF data from the incoming SeRF stream, if needed, at FPGA 403. In this embodiment, FPGA 403 is a logic device that is programmed to convert serial digital data into RF sampled data and programmed to convert RF sampled data into serial digital data. DART module 400 then converts the digital signal to analog with digital to analog converter (DAC) 408. Transmission path 404 continues as DART module 400 filters, amplifies and up-converts the analog signal for RF transmission with an assortment of filters 410, amplifiers 412, an oscillator 414, and an attenuator 416. The transmission path exits DART module 400 at an SMA connector 420. The signals travel in the opposite direction down reception path 406, where they are converted from analog to digital and sent to a SeRF communicator. First signals are received at SMA connector 420. DART module 400 then amplifies, down-converts, filters the incoming RF signal with a plurality of filters 410, amplifiers 412, oscillators 414, and attenuators 416. DART module 400 then digitizes the signal with analog to digital converter 422. FPGA 403 then forms a SeRF stream and provides the SeRF stream as parallel digital RF sampled data to a SeRF communicator.
FIG. 5 illustrates a schematic view of one embodiment of a SeRF communicator 500 for use in either host unit 102 or remote unit 106. Serial radio frequency communicator 500 has a plurality of optical input/outputs 502, a clock 504, a field programmable gate array (FPGA) 506, a plurality of DART links 508, and a processor 510. In this embodiment, SeRF communicator 500 has eight (8) optical input/outputs 502. Optical input/outputs 502 connect to optical fiber which is used as a transport mechanism, or optical fiber that links SeRF communicator 500 to an optical multiplexer or a millimeter waver or microwave transceiver. Optical input/outputs 502 receiver high speed serial data transmission from another SeRF communicator. In addition, optical input/outputs 502 receive Open Base Station Architecture (OBSAI) protocol data from a baseband unit. In one embodiment, to aid in the ability of optical input/outputs 502 to receive multiple data formats, the signals received from optical input/outputs 502 are transmitted at the same frequency which is set to match the OBSAI protocol. Also, OBSAI data is stripped at the data link layer with a 8B/10B encoder to provide a good ones and zeros balance and remove approximately 20 percent of the OBSAID overhead. Finally, 16-bit filler words are used to provide a 24/25ths transport ratio and match a 2.94 GBps transport speed to enable transport of OBSAI or SeRF data. The OBSAI protocol data is explained in more detail below with reference to FIG. 6. Optical input/outputs 206, also conform to the optical small form-factor pluggable multi-source agreement. Alternatively, any frequency of signal or shape of connector could be used as is known in the art. SeRF communicator 500 has eight (8) optical input/outputs and DART links 508 for 8 separate DART modules which transmit RF sampled data to/from DART modules.
In one embodiment, DART links 508 and corresponding connectors on a DART interface carry 6 slots of digitized RF payload for reading and writing DART FPGA registers from SeRF FGPA 506. Each slot consists of 16 bits: 15 bits of digitized RF and 1 overhead bit used to transfer FPGA register data. The slots are framed in groups of 6 16-bit words, with each slot repeating at the sampling rate of 15.36M samples per second. A “superframe” of 32 frames encapsulates the data payload and provides synchronization. Thus, in this embodiment DART links 508 are 16-bit parallel data streams. In another embodiment, DART links 508 are serial. FPGA 506 has eight SERDES to serialize and de-serialize each data stream. Thus, there is one SERDES running for each DART link 508 and optical input/output 502. In this embodiment, each SERDES runs at either half rate or full rate and 50% efficiency such that the SERDES offers 6 RF slots of data. In another embodiment, there are half as many SERDES as DART modules. Thus, the SERDES run at full rate, 100% efficiency and offer 12 RF slots of data.
In one direction, SeRF communicator 500 receives incoming SeRF streams over DART links 508 from DART modules, assembles data frames, and sends an outgoing optical serial data stream through optical input/outputs 502. In the other direction, SeRF communicator 500 receives an optical serial data stream from another SeRF communicator at optical input/outputs 502. SeRF communicator 500 then disassembles the frames of the serial data stream, and provides SeRF streams over DART links 508 to DART modules. SeRF communicator 500 also performs splitting and summing for digital simulcast, and provides a user interface for alarm, status, or configuration management. SeRF communicator 500 also provides bi-directional conversion to/from OBSAI protocol data received at optical input/outputs 502 from/to RF sampled data for DART modules. Additionally, SeRF communicator 500 has at least one RJ-45 connector 216 for receiving IP packets. In one embodiment, RJ-45 connector 216 supports Gigabit Ethernet.
Along with being configurable to communicate on different frequency band/sub-bands and with different technologies, host unit 102 and remote unit 106 are configurable to perform more or less of the wireless processing of the RF signal. Host unit 102 and remote unit 106 are configurable into three different functional configurations. The first configuration is illustrated in FIG. 1 and has host unit 101 and remote unit 106 functioning as a range extender for base station 101. In this configuration, backhaul data is transmitted between host unit 102 and remote unit 106. The second configuration is illustrated in FIG. 6, and has fronthaul data transmitted between host unit 102 and remote unit 106. In this configuration remote unit 106 performs the functionality of a base station. The third configuration is illustrated in FIG. 7 and has ‘midhaul’ data transmission between host unit 102 and remote unit 106. In this embodiment, ‘midhaul’ data refers to OBSAI protocol data or similar partially processed wireless signals. Each of the three configurations will now be explained in further detail.
Referring back to FIG. 1, system 100 shows one configuration for connection of host unit 102 and remote unit 106 in which remote unit 106 functions as a range extender. In this option, base station 103 contains all necessary components to convert IP packets received from an Internet gateway into an analog bit stream for transmission over antenna 108. Except for needed amplification, the signal is ready for transmission over antenna 108 once sent by base station 103. Host device 102 and remote device 106 do not perform any further processing on the data except what is required to send and receive the data over long range transmission. Host unit 102 contains the components as illustrated in FIG. 2 and receives the analog signal from base station 103 at the DART module matching the analog signal frequency band and technology. Host unit 102 converts the signal and transmits the data over transport mechanism 104. Remote unit 106 contains the components as shown in FIG. 3. Remote unit 106 receives the signal from transport mechanism 104 and sends the data to the DART module matching the frequency band and technology. The signal is then converted and transmitted over antenna 108 to mobile users.
FIG. 6 shows another configuration of a system 100 where base station functionality is performed at remote unit 106. This configuration provides increased capacity to a network of antennas by allowing each remote unit 106 to function as a base station. In this embodiment of system 100, IP data is not processed by a base station before sending to remote unit 106. Instead IP data is received at host unit 102 directly from IP gateway 101. IP data is received at an RJ-45 connector on SeRF communicator 202 of host unit 102. In this configuration, therefore, the signal does not travel through DART module 208, 210, 212 of host unit 102. The IP data is converted to a serial optical stream and transmitted over transport mechanism 104 to remote unit 106. Remote unit 106 receives the IP data at SeRF communicator 302.
Remote Unit 106, in this embodiment, has a baseband unit 602 which is connected to a slot of DART interface 306. In this configuration, baseband unit 602 is in fact a remote WiMax base station which replaces the functionality of base station 103 in the first configuration. SeRF communicator 302 converts the packetized optical data received into 25-75 Mbps data and sends the data over to baseband unit 602. Baseband unit 602 performs baseband processing to put the IP data onto a channel. Baseband unit 602 also creates the protocol and modulation type for the channel. Baseband unit 602 then converts the data to match the OBSAI protocol. This OBSAI data is sent back into an optical input/output 502 of SeRF communicator 302. SeRF communicator 302 uses software to convert the OBSAI protocol data into digital RF sampled data and sends the digital RF data to DART module 308 for transmission over antenna 108. In another embodiment, baseband unit 602 converts IP data to/from common public radio interface (CPRI). Alternatively, any digital baseband protocol, including standard and proprietary protocols, or any software defined radio interface could be used by baseband unit 602 and SeRF communicator 302.
FIG. 7 illustrates yet another configuration of a system 100 in which remote unit 106 performs the functionality of a base station, and the baseband processing is performed prior to transmission by host unit 102. In this embodiment, IP data is received at a baseband unit 702 which converts the IP data into data conforming to the OBSAI protocol. Alternatively, any of the protocols listed with respect to FIG. 6 could be used. The OBSAI protocol data is sent to host unit 102 and OBSAI protocol data is transmitted over transport mechanism 104. In another embodiment, the OBSAI conversion is done in SeRF 202 of host unit 102 before the serial data is transmitted to remote unit 106. Here again, DART module 208 is not used at host unit 102, since the data has not been converted to RF yet. The OBSAI protocol data is received by remote device 106 at SeRF communicator 302. SeRF communicator 302 converts the OBSAI protocol data into digital RF sampled data and interfaces with DART 308. DART 308 converts the data to analog RF and the signal is sent over antenna 108.
Since host unit 102 and remote unit 106 have multiple input/outputs and can have multiple types of DART modules connected to each, host unit 102 and remote unit 106 are configured to multiplex different functional configurations through different input/outputs simultaneously. Thus, in one embodiment, a first input/output of host unit 102 and remote unit 106 function as a range extender for a base station. A second input/output of host unit 102 and remote unit 106 function to transmit ‘midhaul’ data. At the same time a third input/output of host unit 102 and remote unit 106 functions to transmit fronthaul data and remote unit 106 performs baseband processing upon the data.
The modular design of modular wireless communications protocol allows many different combinations of transport mechanisms, frequency bands, communication technologies, and processing functionality to operate simultaneously on the same host unit and remote unit.
Placing a base station at a remote wireless communication stations such as described with the configuration of FIG. 6 allows service providers to set up a distributed base station system. FIG. 8 illustrates one embodiment of a distributed base station system 800. System 800 has a central node 801 having an IP gateway and a plurality of remote wireless communication stations 802, 804, 806, 808, 810, 812. Each remote station 802, 804, 806, 808, 810, 812 includes a remote unit 814, 816, 818, 820, 822, 824, an antenna 826, and a router 828. In this embodiment, remote unit 818 and remote unit 820 are configured into a WiMax compatible base station. In another embodiment, all remote units 814, 816, 818, 820, 822, 824 are configured into PCS cellular base stations. Alternatively, any number of remote units 814, 816, 818, 820, 822, 824 could be configured into a base station for any of the technology or frequency bands described with respect to system 100. Each remote station 802, 804, 806, 808, 810, 812 functions similarly, except that they will vary based on the configuration of their respective remote unit 814, 816, 818, 820, 822, 824.
Distributed base station system 800 has many advantages over traditional centralized base station systems. For example, remote stations 806, 806 which are equipped with a base station do not need to transmit signals back to central node 801 for base station processing. Instead, when an RF signal is received via antenna 826 at remote station 806, for example, remote station 806 processes the RF signal with remote unit 818, which is configured as a base station. Processing the RF signal forms a second RF signal which is then routed toward the destination of the RF signal. In this embodiment, the RF signal received at remote unit 806 is from a first mobile device which is in communication with a second mobile device which is the destination of the second RF signal. In another embodiment, the RF signal is received from a fixed internet user and the destination of the second RF signal is on the internet via IP gateway at central node 801. In this embodiment, the second mobile device is within transmission range of remote station 812. Thus, after processing by remote unit 818 at remote station 806, routers 828 at remote stations 806, 810, 812 route the second RF signal through remote station 810 to remote station 812. Thus, distributed base station system 800 simplifies and speeds up the processing of wireless signals.
In addition, there are many other advantages of a distributed base station system. For example, since each remote station 802, 804, 806, 808, 810, 812 includes a router, a best path is found to the from the origination remote station to the destination remote station. This decreases the latency of communication transmission, and also reduces unnecessary network traffic. In addition, in one embodiment where each remote station 802, 804, 806, 808, 810, 812 is equipped with a base station, each remote station 802, 804, 806, 808, 810, 812 obtains dedicated capacity to the system. Dedicated capacity refers the allocation of an unvarying amount of bandwidth to each remote station 802, 804, 806, 808, 810, 812. For example, in one embodiment, each remote station 802, 804, 806, 808, 810, 812 is allocated 25 Mbps of bandwidth. This is not possible in previous systems, because each remote station shares the capacity of a single central base station.
In one embodiment, remote stations 802, 804, 806, 808, 810, 812 are set up in a ring configuration as shown in FIG. 8. The ring structure is advantageous, because a ring configuration allows multiple paths to be found to each remote station 802, 804, 806, 808, 810, 812. Thus, there are more options for a best path to be found to each remote device 802, 804, 806, 808, 810, 812, and congested areas are more easily avoided. In another embodiment, shown in FIG. 9, remote stations 902, 904, 906, 908, 910, 912 are arranged into tree configurations. Tree configurations are advantageous, because they reduce the complexity of the network and the amount of communication links that must be established. Tree configurations, however, still provide reduced latencies by allowing signals to be routed through the local hubs (e.g. remote station 902 and 908) and not requiring transmission to central hub 901.
In yet another embodiment, a plurality of remote stations is set up in a daisy chain configuration. Alternatively, any combination of ring, tree, or daisy chain configurations could be used to network a plurality of remote stations.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.

## Claims

1. A modular wireless communications platform comprising:
a modular host unit comprising:
a host serial radio frequency (SERF) communicator having a logic device programmed to convert reverse path serial digital data into reverse path host-side RF sampled data and programmed to convert forward path host-side RF sampled data into forward path serial digital data; and
a host interface coupled to the host SERF communicator, the host interface including a plurality of host digital to analog radio frequency transceiver (DART) connectors, each host DART connector configured to connect with an edge connector of one of a plurality of host DART modules configured to transmit RF signals to a base station and receive RF signals from the base station, wherein the host SERF communicator is configured to send the reverse path host-side RF sampled data through at least one of the host DART connectors to at least one of the host DART modules, wherein the modular host unit is field configurable such that other host DART modules can be inserted into each host DART connector to enable operation with different frequency bands or communication technologies; and
a modular remote unit in communication with the modular host unit comprising:
a remote SERF communicator configured to convert the forward path serial digital data into forward path remote-side RF sampled data and configured to convert reverse path remote-side RF sampled data into the reverse path serial digital data; and
a remote interface coupled to the remote SERF communicator, the remote interface including a plurality of remote DART connectors, each remote DART connector configured to connect with an edge connector of one of a plurality of remote DART modules, wherein the remote SERF communicator is configured to send the forward path remote-side RF sampled data through at least one of the remote DART connectors to at least one of the remote DART modules, wherein the modular remote unit is field configurable such that other remote DART modules can be inserted into each remote DART connector to enable operation with different frequency bands or communication technologies.

2. The modular wireless communications platform of claim 1, wherein the host SERF communicator of the modular host unit further comprises:
a plurality of host optical input/outputs, coupled to the logic device, configured to communicate the forward path serial digital data and the reverse path serial digital data; and
a plurality of host DART module links, coupled to the logic device, configured to communicate the forward path host-side RF sampled data and the reverse path host-side RF sampled data; and
wherein the remote SERF communicator of the modular remote unit comprises:
a plurality of remote optical input/outputs configured to communicate the forward path serial digital data and the reverse path serial digital data; and
a plurality of remote DART module links configured to communicate the forward path remote-side RF sampled data and the reverse path remote-side RF sampled data.

3. The modular wireless communications platform of claim 1, wherein the modular remote unit further includes a removable baseband unit coupled to the remote SERF communicator, wherein the removable baseband unit is configured to perform baseband processing on IP data and place the IP data onto a channel for the remote SERF communicator.

4. A modular remote radio head comprising:
a serial radio frequency (SERF) communicator having a logic device programmed to convert forward path serial digital data from a host unit, which receives RF signals from a base station into forward path remote-side RF sampled data and programmed to convert reverse path remote-side RF sampled data into reverse path serial digital data;
at least one first connector configured to accept insertion of an edge connector of a digital to analog radio frequency transceiver (DART) module, wherein the DART module is programmed to convert the forward path remote-side RF sampled data to forward path analog RF data and is programmed to convert reverse path analog RF data to the reverse path remote-side RF sampled data, the at least one first connector configured to couple the transceiver DART module to the SERF communicator;
at least one second connector configured to couple to an amplifier and configured to couple the amplifier to the DART module;
at least one third connector configured to couple to a duplexer and configured to couple the duplexer to the amplifier; and
an antenna coupled to the duplexer.

5. The modular remote radio head of claim 4, wherein the SERF communicator further comprises:
a plurality of optical input/outputs configured to communicate the forward path serial digital data and the reverse path serial digital data; and
a plurality of digital DART module links configured to communicate the forward path remote-side RF sampled data and the reverse path remote-side RF sampled data.

6. The modular remote radio head of claim 4, wherein the frequency transceiver DART module is programmed to transmit the forward path analog RF data within a certain frequency band and is programmed to receive the reverse path analog RF data within the certain frequency band.

7. The modular remote radio head of claim 4, wherein the frequency transceiver DART module is plugged into the at least one first connector.

8. The modular remote radio head of claim 4, wherein the SERF communicator is configured to convert the forward path serial digital data into the forward path remote-side RF sampled data and to convert the reverse path remote-side RF sampled data into the reverse path serial digital data for multiple DART modules.

9. The modular remote radio head of claim 8, wherein the multiple DART modules include different types of digital DART modules that communicate using different protocols or on different frequency bands.

10. The modular remote radio head of claim 4, further comprising
an optical multiplexer connected to the SERF communicator, wherein the optical multiplexer is configured to multiplex optical signals to a host unit from the SERF communicator or from the host unit to the SERF communicator.

11. The modular remote radio head of claim 4, further comprising
a removable baseband unit coupled to the SERF communicator, wherein the removable baseband unit is configured to perform baseband processing on IP data and place the IP data onto a channel for the SERF communicator.

12. A modular remote radio head for a wireless communication system comprising:
a serial radio frequency (SERF) communicator having a logic device programmed to convert forward path serial digital data from a host unit, which receives RF signals from a base station into forward path remote-side RF sampled data and programmed to convert reverse path remote-side RF sampled data into reverse path serial digital data; and
an interface having a plurality of connectors configured to connect to a plurality of edge connectors of a plurality of digital to analog radio frequency transceiver (DART) modules, wherein the DART modules are programmed to convert the forward path remote-side RF sampled data into forward path analog RF data and are programmed to convert reverse path analog RF data into the reverse path remote-side RF sampled data, and wherein the interface is coupled to the SERF communicator and configured to allow transfer of the forward path remote-side RF sampled data from the SERF communicator to the plurality of digital DART modules when plugged into the plurality of connectors.

13. The modular remote radio head of claim 12, wherein the DART modules are different types of DART modules, wherein each DART module of the different types of digital DART modules ere is configured to operate in a different respective frequency band or according to a different respective communication protocol.

14. The modular remote radio head of claim 12, wherein the SERF communicator is configured to transmit the reverse path serial digital data and receive the forward path serial digital data as high speed optical signals.

15. The modular remote radio head of claim 12, wherein the SERF communicator is configured to send the forward path remote-side RF sampled data to and receive the reverse path remote-side RF sampled data from the DART modules.

16. The modular remote radio head of claim 12, wherein the SERF communicator is configured to send the forward path serial digital data and receive the reverse path serial digital data as backhaul data such that the modular remote radio head functions as a range extender.

17. The modular remote radio head of claim 12, wherein the modular remote radio head further comprises a baseband unit, coupled to the SERF communicator, the baseband unit configured to process fronthaul data and cause the modular remote radio head to function as a remote base station.

18. The modular remote radio head of claim 12, wherein the modular remote radio head is configured to convert between fronthaul data and the forward path remote-side RF sampled data for a first transceiver DART module and to convert between backhaul data and the reverse path remote-side RF sampled data for a second DART module.

19. A modular remote radio head for a wireless communication system comprising:
a serial radio frequency (SERF) communicator comprising:
at least one optical input/output configured to receive and send serial digital data from/to a host unit, the host unit configured to receive and send RF signals from/to a base station;
a plurality of digital to analog radio frequency transceiver (DART) module links configured to transport digital RF sampled data;
wherein the SERF communicator is configured to multiplex and demultiplex signals between the plurality of digital transceiver DART module links and the at least one optical input/output; and
an interface including a plurality of DART connectors coupled to respective ones of the plurality of DART module links of the SERF communicator, each of the DART connectors is connected to an edge connector of one of a plurality of digital to DART modules such that the modular remote radio head is field configurable and other DART modules can be inserted into each DART connector to enable operation with different frequency bands or communication technologies, wherein the frequency transceiver plurality of DART modules provide bi-directional conversion between analog RF data and the digital RF sampled data.

20. The modular remote radio head of claim 19, wherein the SERF communicator further comprises at least one RJ-45 connector configured to send and receive IP packets from a host unit, wherein the serial SERF communicator is programmed to convert the IP packets to and from the digital RF sampled data for the plurality of digital transceiver DART modules.