Abstract:
Various embodiments of a millimeter-wave wireless point-to-point or point-to-multipoint communication system which maintains a stable communication link even in the face of problems such as vibration or other mechanical disturbance to transceivers in the system or radio interference to the transmission beam produced by a transmitter and received by a receiver. The system comprises a transmitter, a receiver, a high-gain antenna, and allied equipment as described. In various embodiments, a beam is mechanically or electronically redirected to improve system performance. In various embodiments, the modulation schemes or coding schemes of the transmission are altered to improve system performance.

Description:
BACKGROUND 
       [0001]    In PTP and PTMP networks, transceivers at remote points are aligned with each other, such that a directional connection is achieved. However, all point-to-point (“PTP”) and point-to-multipoint (“PTMP”) wireless communication networks suffer from problems of link degradation. Such problems may be temporary or permanent. Such problems may be caused by vibration or other movement in the transmission pole, tower, or other structure that supports the radio transceivers. Such problems may also be caused by electromagnetic interference or other problems, either temporary or permanent, in the radio environment around the link. 
         [0002]    The problem or vibration or other movement can arise from a variety of causes, including, among others, wind, vibration from passing vehicles, or shifting ground in which the supporting structure is anchored. Over time, the supporting structure may be subject to metal fatigue or other mechanical stress, which can exacerbate the condition, and increase the effects of the causative factors. If there is too much vibration at one of the transceivers, there will be too much movement in that transceiver for it to maintain communication with one or more of its matched remote transceivers. The result is a breakdown of communication during the time of the vibration. This problem is particularly severe in millimeter-wave communication networks, but the problem is not limited to such networks. 
         [0003]    Solutions that have been offered to these mechanical problems included mechanical means of reducing vibration of the transceivers. One example would be the use of a stronger kind of material in the supporting structure. A second example would be the use of a more non-corrosive kind of material in the supporting structure. A third example would be the thickening, or otherwise strengthening, of the material in the supporting structure. A fourth example would be adding lines to the supporting structure, such as metal cables, buttresses, and the like. A fifth example would be the driving of the support structure deeper into the ground. A sixth example would be to add a kind of root system in that part of the structure beneath the level of the ground. These are all mechanical solutions. They can reduce the severity of the problem, but they cannot solve the problem. Even with these solutions, vibrations in transceivers of PTP and PTMP networks continue to create communication difficulties in such networks. 
         [0004]    The problem of electromagnetic interference or other environmental disturbance may be caused by a great variety of causes, including, for example, solar radiation, or other radio transmissions in the area, radiation generated by power lines or electric motors, competing radio transmissions, or other causes. These problems, which are often of a temporary nature, are often solved by building into a communication link budget sufficient excess to deal with such problems. This solution is limited in that it is unable to deal with severe problems. It is also deficient in that it requires additional material, energy, and expense to be deployed on a permanent or semi-permanent basis, when in fact the problem, whatever its severity, may be of a temporary nature. 
       SUMMARY 
       [0005]    Described herein are systems and methods in PTP and PTMP wireless communication networks, wherein the network is engineered in such a manner as to maintain communication between remote transceivers, even in the face of problems such as vibrations, other mechanical problems, or electromagnetic interference, affecting one or more of such transceivers. 
         [0006]    One embodiment is a millimeter-wave communication system that operates to optimize beam direction together with modulation and coding schemes. In one particular form of such an embodiment, the system includes a millimeter-wave receiver, and a millimeter-wave transmitter that is located away from the receiver and that maintains a wireless data link with the receiver via a millimeter-wave radio beam generated by a directional antenna that can generate the beam toward various configurable directions. In this particular form of such an embodiment, system is further operative to: (i) aim the millimeter-wave beam toward different directions, (ii) measure the performance of the wireless data link toward the different directions, (iii) set the beam toward the one of the directions that results in essentially the best system performance; and (iv) optimize further performance of said wireless data link by selecting modulation and coding schemes for the wireless data link. Such schemes may be selected according to one or more of various criteria. 
         [0007]    One embodiment is a method for optimizing performance of a millimeter-wave communication system in which a wireless data link is conveyed via a beam of millimeter waves. In one particular form of such embodiment, the system detects degradation in the performance of a wireless data link. The system then performs a test procedure by changing, at least temporarily, the direction at which the transmitted beam is pointing, and measuring the resulting performance. According to a result of the test procedure, the system then selects a course of action for at least partially resolving the degradation. The selection is made from essentially two possible courses of action, in which the system may select either one action or the other, or rather both actions. One of these possible courses of action is optimizing the direction at which the beam is pointing. The second of these possible courses of action is optimizing modulation and coding schemes of the wireless data link. 
         [0008]    One embodiment is a method for setting beam direction together with modulation and coding schemes in a millimeter-wave communication system. In one particular form of such embodiment, the system optimizes performance of a wireless data link during idle periods of the wireless data link. In some embodiments, performance is optimized by (i) aiming toward different directions a narrow millimeter-wave beam that conveys the wireless data link, (ii) measuring performance of the wireless data link toward the different directions, and (iii) setting the direction of the narrow millimeter-wave beam toward the measured direction that results in essentially the best performance of the system. In some embodiments, the system further optimizes performance of the wireless data link, by selecting modulation and coding schemes of the wireless data link such that substantially maximum data transmission rates are achieved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The embodiments are herein described, by way of example only, with reference to the accompanying drawings. No attempt is made to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the embodiments. In the drawings: 
           [0010]      FIG. 1A  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system; 
           [0011]      FIG. 1B  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system with a radiation beam; 
           [0012]      FIG. 1C  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system in which the direction of a radiation beam has been changed one or more times to allow a test procedure to be performed; 
           [0013]      FIG. 1D  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system, with a radiation beam whose direction has been optimized on the basis of results from a test procedure; 
           [0014]      FIG. 1E  illustrates one embodiment of potential combinations of modulation schemes and coding schemes in a millimeter-wave point-to-point (“PTP”) communication system; 
           [0015]      FIG. 2  illustrates one embodiment of electronic redirection of a radio beam by a phased array in a millimeter-wave point-to-point (“PTP”) communication system; 
           [0016]      FIG. 3A  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system, with a radiation beam in a direction before mechanical change in the direction of the beam; 
           [0017]      FIG. 3B  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system, with a radiation beam in a direction after mechanical change in the direction of the beam; 
           [0018]      FIG. 4  illustrates a flow diagram describing one method for optimizing system performance in a millimeter-wave point-to-point (“PTP”) communication system; and 
           [0019]      FIG. 5  illustrates a flow diagram describing one method for setting beam direction together with modulation schemes and coding schemes, in a millimeter-wave point-to-point (“PTP”) communication system. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Throughout this written description and the claims, the term “beam” is exactly the same thing as “radiation pattern”. In all cases, the intent is that the transmission of a transmitter mounted on a supporting structure in a PTP or PTMP system, creates a particular configuration or pattern or radiation energy. 
         [0021]    Throughout this written description and the claims, a “non-idle period” is a period of time during which a communication system is transmitting in an ordinary manner. 
         [0022]    Throughout this written description and the claims, “reducing a level of modulation” means to change a modulation scheme such that after the change the data rate is lower, but the quality of the link (also known as the “robustness of the link”) is higher. Similarly, throughout this written description and the claims, “reducing a coding rate” means to change a coding rate such that after the change the data rate is lower, but the quality of the link (also known as the “robustness of the link”) is higher. 
         [0023]    Throughout this written description and the claims, “MCS” is short for “modulation and coding schemes”. Exemplary but non-limiting modulation schemes discussed herein include QPSK and QAM, but it is understood that any communication modulation scheme would be acceptable. Exemplary but non-limiting coding rates associated with coding schemes discussed herein include ½, ⅔, ¾, and ⅚, but it is understood that any communication coding scheme would be acceptable. Examples of coding schemes include RS and Turbo codes or any forward error correction scheme or any erasure coding scheme. Although the term “MCS” including both the modulation schemes and the coding schemes, it is understood that in alternative embodiments it is possible to alter the modulation scheme but not the coding scheme, or the coding scheme but not the modulation scheme, or both the modulation scheme and the coding scheme. 
         [0024]    Throughout this written description and the claims, “PTP” is short for “point-to-point”, and signifies a wireless communication system in which there is communication between a transmitter and a receiver which are located remotely from one another, and in which the planned communication path between the transmitter and the receiver is the “central path”. 
         [0025]    Throughout this written description and the claims, “PTMP” is short for “point-to-multipoint”, and signifies a wireless communication system in which there is communication between a transmitter and each of two or more receivers, all of which receivers being located remotely from the transmitter, and in which the planned communication path between the transmitter and a particular receiver is the “central path” for that pair of transmitter and receiver. 
         [0026]      FIGS. 1A ,  1 B,  1 C,  1 D,  1 E,  2 ,  3 A, and  3 B, inclusive, illustrate various embodiments of millimeter-wave communication systems. 
         [0027]      FIG. 1A  illustrates one embodiment of a millimeter-wave communication system  100 . In  FIG. 1A , the millimeter-wave communication system  100  includes a transmitter  101  which itself includes an antenna with a dish reflector  105 , and a receiver  102 . There is a link  103 , which is conveyed over a directional beam from transmitter  101  to receiver  102 . 
         [0028]      FIG. 1B  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system  100  with a radiation beam  105   a . In  FIG. 1B , the millimeter-wave communication system  100  includes a transmitter  101  which itself includes an antenna with a dish reflector  105 , and a receiver  102 . The transmitter is transmitting a signal in the form of a radiation beam  105   a , where the receiver  102  is located substantially in the center of the radiation beam  105   a.    
         [0029]      FIG. 1C  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system  100 , which includes a transmitter  101  which itself includes and antenna with a dish reflector  105 , in which the direction of a radiation beam has been changed one or more times to allow a test procedure to be performed. The original direction of the beam is shown as  105   b . When the antenna with dish reflector  105  is pointed up or electronically steered up, the pointed up direction of the beam is shown in  105   b   1 . When the antenna with dish reflector  105  is pointed down or electronically steered down, the pointed down direction of the beam is shown in  105   b   2 . The system  101  tests the quality of the link  103  in each of the three beam directions,  105   b ,  105   b   1 , and  105   b   2 . 
         [0030]      FIG. 1D  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system  101 , with a radiation beam  105   a  whose direction has been optimized on the basis of results from a test procedure. The optimized beam  105   b  opt is the beam in a direction such that the communication link  103  between the transmitter  101  and the receiver  102  is optimized. Although receiver  102  is not shown in  FIG. 1D , it is understood that receiver  102  is located substantially in the middle of optimized beam  105   bopt.    
         [0031]      FIG. 1E  illustrates one embodiment of potential combinations of modulation schemes and coding schemes (MCS)  106  in a millimeter-wave point-to-point (“PTP”) communication system  100 . In  FIG. 1E , three modulation schemes are shown, which are QPSK, QAM-16, and QAM-64. It is understood that these modulation schemes are exemplary only, and any known modulation schemes could be used. In  FIG. 1E , four coding rates associated with schemes are shown, which are ½, ⅔, ¾, and ⅚. It is understood that these coding rates are exemplary only, and any known coding rates associated with any known coding scheme could be used. The table in  FIG. 1E  arranges the MCS in a particular order, such that a higher lines in the MCS table allows a communication with a lower data rate, but a higher quality, than any of the lower lines. For these purposes, “higher quality” also means “more robust”. QPSK ½ is more robust, but provides a lower data rate, than any of the other MCS possibilities shown in  FIG. 1E . For example, QAM-64 ⅚ is less robust, but provides a higher data rate, than any of the other MCS possibilities shown in  FIG. 1E . For example, QPSK ¾ is less robust but provides a higher data rate than QPSK ½, but conversely QPSK ¾ is more robust but provides a lower data rate than all of the MCS possibilities listed in  FIG. 1E  below QPSK ¾. 
         [0032]      FIG. 2  illustrates one embodiment of electronic redirection of a radio beam by a phased array  105   arr  in a millimeter-wave point-to-point (“PTP”) communication system  100 . In the phased array  105   arr , various patches or slots are shown, arranged in a grid with a horizontal direction and a vertical direction. A phrased array, such as  105   arr , may perform an electronic redirection or steering of a transmission beam  105   a , thereby optimizing the link  103  between a transmitter  101  and a receiver  102 , without mechanically changing the direction of the transmitter antenna  105  or the receiver antenna. In some embodiments, a transmission beam  105   a  is redirected both electronically by a phased array  105   arr , and also by mechanical redirection of either a transmitter  101  or a receiver  102 , or of both the transmitter  101  and the receiver  102 . 
         [0033]    The direction of a transmitter antenna  105  or a receiver antenna may be also be changed using beam-switching techniques. 
         [0034]      FIG. 3A  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system  100 , with a radiation beam  105   a  in a direction before mechanical change in the direction of the beam  105   a . In  FIG. 3A , the transmitter  101 , transmits the beam  105   a  over the antenna with dish  105 , forming the beam shown in  FIG. 3A . 
         [0035]      FIG. 3B  illustrates one embodiment of a millimeter-wave point-to-point (“PTP”) communication system  100 , with a radiation beam  105   a  in a direction after mechanical change in the direction of the beam  105   a . In  FIG. 3B , the antenna with dish  105  has been mechanically redirected such that the direction of the beam  105   a  is lower than the direction of the beam  105   a  shown in  FIG. 3A . It is possible, and occurs in some embodiments, to mechanically alter the direction of the antenna with dish of the receiver  102  rather than the transmitter antenna and dish  105 . In other embodiments, it is possible to mechanically alter the direction of both the transmitter antenna and dish  105 , and the receiver antenna and dish. Any or all of the embodiments of  FIG. 3B  may be enhanced with the addition of changes in the MCS, and in particular, a change to only the modulation scheme but not the coding scheme, or a change to only the coding scheme but not the modulation scheme, or a change to both the modulation scheme and the coding scheme. 
         [0036]    In one embodiment, there is a millimeter-wave communication system  100  operative to optimize the direction of a beam  105   a  together with modulation and coding schemes  106 . The system includes a millimeter-wave receiver  102 , and a millimeter-wave transmitter  101  that is located away from said millimeter-wave receiver  102 . The millimeter-wave transmitter  101  is operative to maintain a wireless data link  103  with the millimeter-wave receiver  102 , via the millimeter-wave beam  105   a . The millimeter-wave transmitter  102  includes a directional antenna  105  which is operative to generate the millimeter-wave beam  105   a  toward various configurable directions  105   b ,  105   b    1 , and  105   b   2 . In one embodiment, the system  100  is further operative to: (i) aim the millimeter-wave beam  105   a  toward different directions  105   b ,  105   b   1 , and  105   b   2 , (ii) measure performance of the wireless data link  103  toward those directions, (iii) set the direction of the millimeter-wave beam  105   a  toward a direction, selected out of the different measured directions, which results in essentially best system performance; and (iv) optimize further performance of the wireless data link  103  by selecting modulation and coding schemes  106  of the wireless data link  103  according to some criterion or criteria. 
         [0037]    In a first alternative embodiment of the millimeter-wave communication system  100  just described, the aiming, measuring, and setting, are done during idle periods of the wireless data link  103 . 
         [0038]    In a second alternative embodiment of the millimeter-wave communication system  100  described above, at least one of the criteria for selecting MCS is a target data transmission rate. 
         [0039]    In a third alternative embodiment of the millimeter-wave communication system  100  described above, at least one of the criteria for selecting MCS is a target bit-error-rate or a target packet-error-rate. 
         [0040]    In a fourth alternative embodiment of the millimeter-wave communication system  100  described above, at least one measure for system performance is a measure of a bit-error-rate or a packet-error-rate. 
         [0041]    In a fifth alternative embodiment of the millimeter-wave communication system  100  described above, at least one measure for system performance is a measure of power received by the millimeter-wave receiver  102  from the millimeter-wave beam  105   a.    
         [0042]      FIG. 4  illustrates one embodiment of a method for optimizing system performance in a In step  1011 : the system  100  detects a degradation in the performance of a wireless link  103  which is being conveyed by the system  100  via a transmitter  101  sending a beam  105   a  of millimeter-waves to a receiver  102 . In step  1012 : the system  100  performs a tests procedure by at least temporarily changing the direction at which the beam  105   a  is pointing. The beam  105   a  is pointing in its original direction  105   b , and is then moved either up  105   b   1  or down  105   b   2 . Any number of up or down changes and tests may be part of the entire test procedure. In step  1013 : the system  100  selects, according to at least one result of the test procedure, a course of action to solve at least partially the degradation. The course of action to be taken is selected from two basic alternatives, which may be chosen alternatively (that is, one alternative but not the other) or collectively (that is, both alternatives together). One alternative course of action is to optimize the direction at which the beam  105   a  is pointed. In this first alternative course of action, the beam  105   a  is directed toward an optimized direction  105   bopt . The optimized direction  105   bopt  may be related to one of the test directions, or it may be a different direction, as per, for example, a fine-tuned direction that may be close to, but not exactly the same as, one of the tested directions. In other words, the directions used in the test procedure may or not include the optimized direction  105   bopt  which is the direction optimized from the first alternative course of action. The second alternative course of action is optimizing the MCS  106  of the wireless data link  103 . Several exemplary, but non-limiting, examples of possible modulation schemes and coding schemes are set forth in  FIG. 1E . 
         [0043]    One embodiment is a method for optimizing performance of a millimeter-wave communication system  100 . The system  100  detects degradation in the performance of a wireless data link  103  conveyed by the system via a beam  105   a  of millimeter-waves between a transmitter  101  and a receiver  102 . The system  100  performs a test procedure which includes at least temporarily changing the direction of the beam  105   a  at least one time from an original direction  105   b  to an up direction  105   b   1  or a down direction  105   b   2 . The direction of the beam  105   a  may be changed any number of times during the test procedure, both up and down, but also sideways, or in any other combination. On the basis of at least one result of the test procedure, the system  100  selects a course of action to resolve at least partially the degradation in performance of the wireless data link  103 . One possible course of action is to change the direction of the beam  105   a  from its original direction  105   b  to either a new direction that is either up  105   b   1  or down  105   b   2 . The new direction chosen may be one of the tested directions, or a different direction. The second possible course of action is to optimize the MCS  106  of the wireless data link  103  by changing either the modulation scheme or the coding scheme, or both the modulation scheme and the coding scheme. The system  100  may select the first course of action, or the second course of action, or both the first and the second courses of action. 
         [0044]    In a first alternative embodiment to the method just described, the system  100  executes the course of actions or courses of actions selected. The result is that the degradation in the performance of the wireless data link  103  is resolved at least partially. 
         [0045]    In a second alternative embodiment to the method for optimizing system performance described above, the performing of the test procedure includes the system  100  changing at least one time the direction at which the beam  105   a  is pointing, and the system  100  determining a level of performance of the wireless data link  103  for at least one of such changed directions. 
         [0046]    In a first possible configuration of the second alternative embodiment just described to a method for optimizing system performance, the selecting of a course of action further includes the system  100  determining that at least one change in direction of the beam  105   a  does not result in resolving at least partially the degradation in performance of the wireless data link  103 , and the system  100  thereby concluding that no change in direction is needed from the original direction  105   b.    
         [0047]    In one possible variation of the first possible configuration just described, the method further includes optimizing the MCS of the wireless data link  103 , thereby at least partially resolving the degradation in the performance of the wireless data link  103 . 
         [0048]    In a second possible option of the first possible variation just described, optimizing the MCS further includes reducing the coding rate of the wireless data link  103 , until the degradation of performance is at least partially resolved. 
         [0049]    In a second possible configuration of the second alternative embodiment just described to a method for optimizing system performance, selecting the course of action further includes the system determining changing direction of the transmitter antenna  105  would resolve at least partially the degradation in performance of the wireless data link  103 , and the system thereby concluding that a change in direction of the transmitter antenna  105  is needed. 
         [0050]    In one possible variation of the second possible configuration just described, the method further includes the system  100  changing a direction at which the beam  105   a  is pointed to at least one of the directions tested, thereby (i) resolving at least partially the degradation in performance of the wireless data link  103 , and also (ii) optimizing the direction at which the beam  105   a  is pointed. 
         [0051]    In a third alternative embodiment to the method for optimizing system performance described above, optimizing the direction at which the beam  105   a  is pointed further includes changing the direction to one of the directions tested during the testing procedure. 
         [0052]    In a first possible configuration of the third alternative embodiment just described, changing the direction at which the beam  105   a  is pointed is done using phased-array techniques. 
         [0053]    In a second possible configuration of the third alternative embodiment described above, changing the direction at which the beam  105   a  is pointed is done by mechanically changing a direction at which a directional transmitter antenna  105  is pointed. 
         [0054]    In a third possible configuration of the third alternative embodiment described above, changing the direction at which the beam  105   a  is pointed is done by using beam-switching techniques. 
         [0055]    In a fourth possible configuration of the third alternative embodiment described above, changing the direction at which the beam  105   a  is pointed is done in only one direction, be it either the vertical direction or the horizontal direction. 
         [0056]    In a fifth possible configuration of the third alternative embodiment described above, changing the direction at which the beam  105   a  is pointed is done in both the vertical and horizontal directions. 
         [0057]    In a fourth alternative embodiment to the method for optimizing system performance described above, performing the test procedure is done during a period of time during which the system  100  does not convey data. 
         [0058]    In a possible configuration to the fourth alternative embodiment just described above, performing the test procedure is done in-between transmission frames belonging to the wireless data link  103 . 
         [0059]    In a fifth alternative embodiment to the method for optimizing system performance described above, performing the test procedure is done during a period of time during which the system  100  conveys data that does not require decoding at reception. 
         [0060]    In a sixth alternative embodiment to the method for optimizing system performance described above, degradation of performance of the wireless data link  103  is caused by an undesired change of direction at which a directional transmission antenna  105  is pointed. 
         [0061]    In a first possible configuration to the sixth alternative embodiment just described above, the undesired change of direction is caused by wind. 
         [0062]    In a second possible configuration to the sixth alternative embodiment just described above, the undesired change of direction is caused by mechanical vibration. 
         [0063]    In a seventh alternative embodiment to the method for optimizing system performance described above, degradation of performance of the wireless data link  103  is caused by weather conditions. 
         [0064]    In an eighth alternative embodiment to the method for optimizing system performance described above, the beam  105   a  is a narrow millimeter-wave beam, thereby making the system  100  particularly susceptible to undesired variations in directions toward which the beam  105   a  is directed. 
         [0065]    In a first possible configuration to the eighth alternative embodiment described just above, the narrow millimeter-wave beam has a vertical beam-width or a horizontal beam-width of less than 10 degrees. 
         [0066]    In a second possible configuration to the eighth alternative embodiment described just above, the narrow millimeter-wave beam has a vertical beam-width or a horizontal beam-width of less than 5 degrees. 
         [0067]    In a third possible configuration to the eighth alternative embodiment described just above, the narrow millimeter-wave beam has a vertical beam-width or a horizontal beam-width of less than 2 degrees. 
         [0068]    One embodiment is a method for setting beam direction together with modulation and coding schemes in a millimeter-wave communication system. In one particular embodiment, the method includes the system  100  optimizing performance of a wireless data link  103  belonging to the system  100 , during idle periods of the wireless data link  103 . The system  100  may do this by (i) aiming a narrow millimeter-wave beam  105   a , operative to convey said wireless data link  103 , toward different directions  105   b ,  105   b   1 ,  105   b   2 , (ii) measuring performance of the wireless data link  103  toward such directions, and (iii) setting a direction of the narrow millimeter-wave beam  105   a  toward a direction, selected out of such different directions, which results in essentially the best performance of the system. The method also includes the system  100  further optimizing performance of the wireless data link  103  by selecting modulation and coding schemes  106  of the wireless data link  103  so as to result in substantially maximum data transmission rates. 
         [0069]    In a first alternative embodiment of the method just described for setting beam direction and MCS, further optimizing performance of the wireless data link  103  in non-idle periods of the wireless data link. 
         [0070]    In a second alternative embodiment of the method described above for setting beam direction and MCS, the method further includes repeating the steps of optimizing and further optimizing the performance of the wireless data link  103 , thereby assuring substantially optimal performance of the wireless data link  103  over extended periods of time. 
         [0071]    In a first possible configuration of the second alternative embodiment of the method described above for setting beam direction and MCS, the method further comprises the system  100  resolving a condition in which the direction of the narrow millimeter-wave beam  105   a  drifts over time. 
         [0072]    In a second possible configuration of the second alternative embodiment of the method described above for setting beam direction and MCS, the method further comprises the system  100  resolving a condition in which the direction of the narrow millimeter-wave beam  105   a  changes suddenly. 
         [0073]    In a third possible configuration of the second alternative embodiment of the method described above for setting beam direction and MCS, the method further comprises the system  100  resolving a condition in which an interference causes a reduction in the power in which the narrow millimeter-wave beam  105   a  is received. 
         [0074]    In a fourth possible configuration of the second alternative embodiment of the method described above for setting beam direction and MCS, method further comprising the system  100  resolving a hybrid condition in which both (i) an interference is causing a reduction of power in which said narrow millimeter-wave beam  105   a  is received, and (ii) the direction of the narrow millimeter-wave beam  105   a  changes suddenly. 
         [0075]    In a third alternative embodiment of the method described above for setting beam direction and MCS, the idle periods of the wireless data link  103  occur in-between transmission frames of such wireless data link  103 . 
         [0076]      FIG. 5  illustrates one embodiment of a method for setting beam direction together with modulation and coding schemes in a millimeter-wave communication system. In step  1021 : the system  100  optimizing performance of a wireless data link  103  belonging to the system  100 , during idle periods of the wireless data link  103 . The system  100  may do this by (i) aiming a narrow millimeter-wave beam  105   a , operative to convey said wireless data link  103 , toward different directions  105   b ,  105   b   1 ,  105   b   2 , (ii) measuring performance of the wireless data link  103  toward such directions, and (iii) setting a direction of the narrow millimeter-wave beam  105   a  toward a direction, selected out of such different directions, which results in essentially the best performance of the system. In step  1022 : the system  100  further optimizing performance of the wireless data link  103  by selecting modulation and coding schemes  106  of the wireless data link  103  so as to result in substantially maximum data transmission rates. 
         [0077]    In this description, numerous specific details are set forth. However, the embodiments/cases of the invention may be practiced without some of these specific details. In other instances, well-known hardware, materials, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. In this description, references to “one embodiment” and “one case” mean that the feature being referred to may be included in at least one embodiment/case of the invention. Moreover, separate references to “one embodiment”, “some embodiments”, “one case”, or “some cases” in this description do not necessarily refer to the same embodiment/case. Illustrated embodiments/cases are not mutually exclusive, unless so stated and except as will be readily apparent to those of ordinary skill in the art. Thus, the invention may include any variety of combinations and/or integrations of the features of the embodiments/cases described herein. Also herein, flow diagrams illustrate non-limiting embodiment/case examples of the methods, and block diagrams illustrate non-limiting embodiment/case examples of the devices. Some operations in the flow diagrams may be described with reference to the embodiments/cases illustrated by the block diagrams. However, the methods of the flow diagrams could be performed by embodiments/cases of the invention other than those discussed with reference to the block diagrams, and embodiments/cases discussed with reference to the block diagrams could perform operations different from those discussed with reference to the flow diagrams. Moreover, although the flow diagrams may depict serial operations, certain embodiments/cases could perform certain operations in parallel and/or in different orders from those depicted. Moreover, the use of repeated reference numerals and/or letters in the text and/or drawings is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments/cases and/or configurations discussed. Furthermore, methods and mechanisms of the embodiments/cases will sometimes be described in singular form for clarity. However, some embodiments/cases may include multiple iterations of a method or multiple instantiations of a mechanism unless noted otherwise. For example, when a controller or an interface are disclosed in an embodiment/case, the scope of the embodiment/case is intended to also cover the use of multiple controllers or interfaces. 
         [0078]    Certain features of the embodiments/cases, which may have been, for clarity, described in the context of separate embodiments/cases, may also be provided in various combinations in a single embodiment/case. Conversely, various features of the embodiments/cases, which may have been, for brevity, described in the context of a single embodiment/case, may also be provided separately or in any suitable sub-combination. The embodiments/cases are not limited in their applications to the details of the order or sequence of steps of operation of methods, or to details of implementation of devices, set in the description, drawings, or examples. In addition, individual blocks illustrated in the figures may be functional in nature and do not necessarily correspond to discrete hardware elements. While the methods disclosed herein have been described and shown with reference to particular steps performed in a particular order, it is understood that these steps may be combined, sub-divided, or reordered to form an equivalent method without departing from the teachings of the embodiments/cases. Accordingly, unless specifically indicated herein, the order and grouping of the steps is not a limitation of the embodiments/cases. Embodiments/cases described in conjunction with specific examples are presented by way of example, and not limitation. Moreover, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope of the appended claims and their equivalents.