Patent Application
20060017626
The present invention relates generally to radio telephony, and more specifically to an external antenna module for a wireless mobile station that may be used to increase receive diversity on the downlink of a CDMA or W-CDMA wireless communication system.
More and more people are using mobile telephones. A telephone is a device that converts sounds, such as a caller's voice, into electrical signals that can be transmitted to another telephone. The receiving telephone detects the transmitted signals and converts them back into sounds that another caller may hear. Typically, each of the telephones involved can both transmit and receive so that the callers may carry on a conversation. Traditional telephones are connected to a telephone network by a wire or cable through which the electrical signals are sent. The telephone network, generally speaking, is a system of interconnected wires and switches that create a transmission circuit from the calling party to the called party. The mobility of a traditional telephone is limited by the wire connecting it to the network.
A mobile phone is basically a portable radiotelephone that communicates with a telephone network using radio-frequency electromagnetic waves to communicate with a network though which call can be routed from source to destination. (The call may or may not be targeted to another mobile phone.) The advantages of a wireless communication system are apparent. Users may take their phones anywhere and use them to make calls, provided there is an appropriate receiving device within range. In many cases, they are even relatively free to move about while actively engaging in a conversation, the network being able to adjust so that the conversation may proceed uninterrupted.
Telephone networks used by mobile phones are similar but not the same as those used by traditional wire-line telephones. As background for application of the antenna module of the present invention, with reference to
Although only three mobile phones are shown in
In addition, as a mobile phone relocates from one geographic area (cell) to another, it may change from communicating through one base station to another one that becomes more suitable utilizing a procedure called handoff (or handover). During a typical handoff procedure, the mobile and two (or more) base stations exchange appropriate control signals so that the transfer may be made with as little inconvenience to the callers as possible. In some systems, simultaneous communication with multiple base stations is used to prevent any noticeable interruption in the conversation.
As this implies, the devices participating in a wireless communication monitor the quality of calls in progress (and other signals) to determine when handoff is appropriate. Quality monitoring may also be used to ensure that a certain level of service (often called “quality of service” or “QoS”) is being maintained. Where a poor-quality transmission results in the complete loss of transmitted information, error checking and correction algorithms are applied so that the transmitting station can be notified and the lost portions can be re-transmitted.
Different QoSs may apply to different kinds of communication sessions. For example, although voice calls have been discussed thus far, wireless networks are increasingly being used for data communication as well so that mobile-phone users can access Internet-based resources, send graphical images, and simply exchange text files. In general, voice calls can tolerate much more error than data transmissions, but they take place in “real time” and therefore do not tolerate interruptions as easily. Data, on the other hand, may arrive divided into packets that can be properly reassembled regardless of their order of arrival—but the information in each packet must be determined with a high degree of accuracy. Some modern applications involve “streaming” audio and video, which is in one sense data that will be used to create a presentation for the user almost as soon as it arrives. In each case, different QoS standards may apply. (Note that while flawless transmission may be the goal, achieving it often comes at great expense, and accepting a lower QoS when it is appropriate to do so may help to conserve system resources.)
Returning to
The cellular network architecture described above has enabled the widespread use of mobile telephones. As previously mentioned, the mobile phones communicating with nearby base stations are required to use far less transmission power than if they were communicating through a distant central antenna. The same, of course, is true of the base-station transmissions as well. (Note that the base stations and other network-infrastructure components are generally, though not necessarily, in communication by some other means than radio-frequency transmission.) The radio channels on the air interface are often defined by a specific radio frequency that is different than those used by other mobile phones and base stations in the area. The use of different frequency channels, often called frequency division multiple access (FDMA) enables numerous mobile stations to communicate with the same base station, for example mobile stations 102 and 103 shown in
To enable even more mobile phone to base station communications to occur in the same cell, each frequency channel may be divided up into a number of time slots. Each time slot recurs periodically and is assigned to a specific communication channel. The time slots are of such duration and recur often enough that even a voice conversation transmitted in this way may appear uninterrupted. This type of multiple access is frequently referred to as TDMA (time division multiple access).
Yet another manner of providing for numerous separate channels in a wireless communication system is the use of spread spectrum technology. In these types of systems, individual transmissions are spread across the entire available frequency spectrum (or a selected portion of it) using a spreading code. A large number of spreading codes are normally made available for this purpose, meaning that a number of different communications may take place in the same frequency band. The target receiver will be able to recognize the spreading code used for any particular transmission, and therefore detects only those transmission intended for it and discards any others. The spreading codes used in a particular area are orthogonal to each other, thus reducing or eliminating the interference between the different channels (some interference will still occur because of non-ideal conditions and other factors).
This type of channelization is often called code division multiple access (CDMA). A variation of CDMA is referred to as wide band CDMA (WCDMA), and involves somewhat different transmission spreading process. Although the specifics of the processes for spreading transmissions in CDMA and WCDMA are not directly relevant to the present disclosure, it is worthy of note that transmissions in such systems are spread somewhat differently in the uplink from those downlink transmissions.
CDMA systems (including WCDMA systems) also rely on power control mechanisms. To further avoid interference, each communicating device (mobile phone or base station) will adjust its power level in order to use the minimal amount of transmission power necessary to transmit a reliable signal. In addition, regulatory agencies often require a limit on the aggregate power used for transmission in any given area. To reduce transmission power to a minimum, measurements of received signals are taken in order to judge the distance to another station, and as an ongoing communication session proceeds, the power level is adjusted as necessary to achieve the desired QoS. Naturally, any other way to reduce the transmission power necessary in a particular cell would also contribute to this advantage, and other methods of reducing power requirements have evolved. One particularly effective method is the use of mobile receive diversity (MRD).
In transmit and receive diversity, certain qualitative advantages have been found in using multiple antennas to transmit and multiple antennas to receive radio signals. Some applications involve sending more than one transmission using each of the available antennas. Others involve sending the same transmission over multiple antennas in order to improve the chances that the signal will be properly received. It is not necessary in all cases that the communicating transmitters and receivers each use an identical number of antennas. MRD is simply the part of this general scheme in which a mobile phone uses multiple antennas for receiving transmissions from a base station or other source. As alluded to above, this improves the transmission QoS and permits lower transmit power to be used. Mobile phones, however, present a particular challenge in the field of receive (or transmit) diversity, because the space available for additional antennas is not unlimited.
Display 220 visually presents certain information for the user's benefit in operating the mobile phone. Scroll key 215 is used to manipulate objects on the display for the user's benefit, and to alter the operation of mobile phone 200 in a predetermined way. Function keys 214 and 216 operate in a similar manner, the effect of their next actuation being displayed on the display 220 so that the user will know which action is being selected. Mobile phone 200 is typically powered by a battery (not shown), but may also be connected to an external power source through power port 225.
Peripheral devices (not shown in
The mobile phone 200 of
Mobile phones have recently increased in popularity for many reasons, some of which have been alluded to above. Naturally, their mobility is often an advantage, and users appreciate the ability to communicate using their own telephone regardless of their location. Initially, however, mobile phones were quite expensive and only used by those who could either afford them or absolutely needed them. Network capacity was limited and quality of service was often poor. The existing infrastructure of several years ago could certainly not have supported the level of traffic that exists today. The increased use of mobile phones, therefore, has been facilitated by advancements both in mobile phone and in network technology that have enabled many mobile phones to effectively communicate at the about same time, even in a relatively small geographic area.
In addition, modern mobile phones can perform many more functions than their predecessors. For example, many mobile phones are now capable of sending and receiving short text messages (sometimes called SMS (short message service) messages). Others can even send email messages. Currently, many networks are even permitting the sending of graphic images and other non-text information. Two mobile devices may even exchange data files that were traditionally exchanged only by hardwire connection. The Internet has for several years been used for this purpose, and many modern mobile phones may now access the Internet for this purpose and to use World Wide Web applications and send email. Naturally, the increased functionality that mobile phones now enjoy has also contributed to their popularity. Needless to say, however, with increased popularity and the number of different applications for which mobile phones can be used, mobile networks constantly need to increase their capacity. At the same time, operators must supply the higher-quality services that consumers are now demanding. Using MRD is one way to do this. Expense and the physical limitations referred to above, however, make universal application of MRD difficult.
Needed is a way to increase the capacity of wireless, and especially CDMA and W-CDMA mobile communications systems by providing an MRD option that overcomes these limitations and is likely to be commercially advantageous. The present invention provides just such a solution.
The present invention provides a way to enable MRD in wireless communication systems without necessarily increasing the cost of basic mobile stations to the operator. To accomplish this objective, the present invention is directed to a detachable external antenna module for use with a wireless mobile station. The mobile station, which typically communicates on a radio frequency channel with a base station connected to the fixed infrastructure of a wireless communication network, may be able to receive transmission from the base station sent at lower power by applying mobile receive diversity (MRD).
In one aspect, the present invention is an antenna module including an antenna element supported by, and preferably totally enclosed in a housing, which housing may also contain radio frequency (RF) receive circuitry. The antenna module may also include other electronics as well, such as power management and authentication-related circuitry. In some embodiments, the antenna module is in a single housing and in other embodiments, more than one housing section may be used. The antenna module of the present invention is intended for use with a mobile phone, and the antenna-module receive circuitry may, in use, be coupled with the digital processor of a mobile phone via an analog-to-digital converter. The antenna module includes a jack for attaching the antenna module to a mobile phone. The jack provides for data, and preferably power links to be established with the mobile phone. Control signals may be passed through the jack as well. The jack preferably holds the antenna module in the desired orientation with respect to the mobile phone, and may permit adjustment in several directions so that the orientation of the antenna element relative to an antenna internal to a mobile phone can be adjusted.
For a more complete understanding of the present invention, and the advantages thereof, reference is made to the following drawings in the detailed description below:
FIGS. 1 though 9, discussed herein, and the various embodiments used to describe the present invention are by way of illustration only, and should not be construed to limit the scope of the invention. Those skilled in the art will understand the principles of the present invention may be implemented in any similar radio-communication device, in addition to those specifically discussed herein.
The present invention is directed to an antenna module for using in connection with a mobile phone that may be used to provide mobile receive diversity (MRD) while at the same time overcoming many of the disadvantages accompanying prior attempts to achieve this result.
In the embodiment of
Note that mobile phones contain circuitry for receiving radio signals and converting them to digital form for processing, at least for their own internal antennas and perhaps for multiple or additional antennas as well. Placing the RF chain in antenna module 300, however, makes it possible to more completely isolate the antenna element 305 (from the internal antenna of the mobile phone). This helps to lower correlation between the antennas and enhances the benefit received from using antenna module 300 to achieve MRD. In an alternate embodiment, however, one or more components of RF chain 315 may be located internally to a mobile phone designed for use with an antenna module without them. In yet another embodiment, RF components may be housed in a device separate from both the mobile phone and the antenna module (instead of or in addition to those present in the antenna module itself). Other components (not shown) may also be included in antenna module 300. For example, a power management function, with appropriate circuitry may be included. Components supporting an authentication function may be present as well.
DSP 445 is, of course, operable to process incoming signals received at antenna element 405. In accordance with the present invention, it is also operable to process signals received at antenna element 305 when antenna element 300 is coupled to mobile phone 400 via data link 330. Moreover, DSP 445 is operable to utilize the signals received at both of the antennas to achieve MRD. Preferably, mobile phone 400 may operate in either mode, that is, with a single antenna or applying MRD, and can switch back and forth from one mode of operation to the other when the antenna module 300 is either removed or connected. In other words, without antenna module 300, mobile phone 400 is nevertheless capable of operation within a wireless communication network. When antenna module 300 is connected to mobile phone 400, DSP 445 processes both signals applying MRD techniques and the benefits of MRD can then be realized. Note, however, that an actual performance improvement, although expected, is not a requirement of the present invention.
In one embodiment, antenna module interface 440 detects when an external antenna module such as antenna module 300 has been attached to mobile phone 400. The data link 330 may be, but is not necessarily established immediately when the external antenna is present. Where the phone is capable of switching to MRD processing even while being used, it is generally preferred that it do so as soon as antenna module 300 is detected. The creation of data link 330 may require only the physical connection of antenna module 300, or a separate switch (not shown) may intervene. In the former case, when the connection is made the signal from antenna module 300 is provided to DSP 445, MRD processing begins.
According to another embodiment of the present invention, a decision must be made to begin MRD processing.
In another embodiment, controller first directs switching circuit 520 to couple the external antenna signal to a test circuit 460. Test circuit 460, though not required, provides the ability to test the incoming signal and it's impact. Testing the incoming signal may, for example confirm that the use of the additional antenna will in fact have a helpful effect on processing. If the antenna is not functioning or is not connected properly, for example, this can be discovered before the input via data link 330 is allowed to affect the signal processing. For another example, if the input from data link 330 is substantially the same as the output of A/D converter 425, then the positive effect of MRD will not be realized.
The test circuit 460 might even be used to compare the outputs of the antenna module antenna and the mobile phone internal antenna and determine which should be used in the event MRD cannot be achieved. In some embodiments, it may also be desirable to inform the user of the results of any signal testing, especially where user confirmation of any change in signal processing is being requested. If the test circuit indicates that the signal arriving from the external antenna module via data link 330 is advantageous to use, then the controller 450 directs that the data link be completed to DSP 445, perhaps after querying the user as described above. Other components may be contained in the interface 440, including for example an analog to digital converter in case one is not present in a given antenna module. Note also, however, that the detector and switch of
Although the configuration of
Similar to the embodiment of
From these illustrations, it should be apparent that other types of relative movement may be achieved with variation in the design of the antenna module housing and connector jack. For one example, the diversity antenna element (represented as 305 in
This flexibility in diversity antenna positioning allows the relative orientation of the multiple antennas to be adjustable. Adjustment by the user is expected, although some designs may encourage adjustment only by a technician. In any case a locking means, or at least some resistance to repositioning, may be provided so that a stable configuration is achievable. Flexibility in antenna configuration provides a way to attempt optimization of the benefits of MRP.
In one embodiment, testing circuit 460 is operable to evaluate be benefit achieved using any particular orientation. Controller 450 monitors this evaluation, and may signal the user (for example using an appropriate indication on display 220) when a relatively advantageous orientation occurs. Although it may not always be practicable for the user to continually readjust the position of the antenna mobile, in other applications there may be a benefit to doing so.
In yet another embodiment, the antenna element itself may be adjusted within the antenna module housing, either physically, electronically, or both. This internal adjustability may be controlled by controller 450 based on the evaluation performed by test circuit 460, permitting automatic adjustment. Where automatic adjustment is enabled, the user may be permitted to override any adjustments, or elect to have the automatic adjustments disabled.
When testing or evaluation of the received signal is performed, the results could also be provided to the network. In this manner, the network becomes aware which stations in its coverage area have this capability. Transmit power calculations may (or may not) take this MRD capability into account. In some applications, it may be advantageous for the network to be able to direct a mobile phone equipped with an antenna module how to use it.
While the mobile phone user benefits by using the antenna module of the present invention, the network operator will also benefit. As MRD increases the QOS for the user, it also permits the base station to transmit with less power and still achieve an acceptable quality level. This lower-power requirement reduces the total power required for communicating with a given number of mobile stations, and therefore increases the capacity of the network (where aggregate power is limited). The external, detachable antenna module of the present invention seeks to provide MRD for a mobile phone using maximum practical antenna isolation to reduce antenna correlation effects.
In addition, using the antenna module of the present invention also means that aside from an antenna module port and the capability to process signals from the additional antenna element, few changes will be required to existing mobile phones. Several options exist for allocating the cost associated with the antenna module itself. First, of course, it could simply be provided with the mobile phone itself, although manufacturers and operators may prefer to sell it as a separate accessory. In some cases, consumers may be willing to bear the cost is a perceivable increase in performance can be obtained. On the other hand, operators needing to increase capacity may simply absorb the additional cost. Some discrimination may be appropriate. An antenna module might be given (or sold) to users who frequent high traffic areas, for example, while those living and working in suburban areas may gain little from its use. Or the antenna modules might be provided for subscribers expected to use their phones a great deal, and for data-intensive applications, as opposed to subscribers who anticipate only occasional voice use.
To encourage subscribers to purchase the antenna module as a separate accessory, incentives may be provided. For example, a lower rate may be applied when the module is used, or used within a high traffic area (in which case use of the antenna module would likely have to be in some way monitored, and perhaps controlled by the system operator). In other cases, the cost may be absorbed in a lower monthly subscription price for a given period, or rebated to customers who remain subscribers for a certain length of time. In any event, offering the antenna module of the present invention makes most or all of these options available, while at the same time improving network capacity.
Note also that different antenna modules may be designed for use with the same mobile phone. In this way, the antenna module may, in addition to (or instead of) providing MRD, make available an antenna suitable for alternate forms of communication. For example, one antenna module may be well-suited for CDMA communications, while another is designed primarily for GSM networks. In another embodiment, an antenna module may include an antenna element for short range communication, such as in a Bluetooth or IEEE 802.111 system. As the number of multi-mode phones increases, being able to select from several antenna module choices might allow for optimization in a variety of environments. Even in a single mode, different antenna modules could be provided so that the best for a particular geographic location can be selected. The separate nature of the antenna module also facilitates, in some cases, the implementation of upgrades. Finally, note that there is no requirement that the antenna module of the present invention be used continuously in all situations, or always used only to provide MRD, even when attached to a mobile phone. Intermittent use, or use in lieu of the main mobile station antenna, may in some situations be desirable.
The preferred descriptions are of preferred examples for implementing the invention, and the scope of the invention should not necessarily be limited by this description. Rather, the scope of the present invention is defined by the following claims.
