CA2789768C - System amd method to control amplifier gain in a radiating line communication system - Google Patents

Abstract

A radio frequency communication has a base station coupled at the first end of a radiating transmission line to send and receive communication signals downstream into the line and upstream from the line. At least two pilot signals are transmitted downstream into the transmission line and each amplifier uses the detected loss of the downstream signal along the section of the transmission line located immediately upstream of the amplifier to predict the anticipate the loss of the upstream signal along the upstream section and amplify the upstream signal to compensate for this anticipated loss.

Description

SYSTEM AND METHOD TO CONTROL AMPLIFIER
GAIN IN A RADIATING LINE COMMUNICATION SYSTEM
FIELD OF THE INVENTION
This invention relates to radio frequency communication systems, and, in particular, communication systems having multi-cascading repeater systems providing a number of bi-directional amplifiers in the system to compensate for losses. In particular, in one aspect, the present invention relates to a radio frequency communication systems utilizing radiating or "leaky" transmission lines and bi-directional amplifiers to amplify the communication signals to and from the base station.
BACKGROUND OF THE INVENTION
Radiating transmission lines are deliberately constructed as imperfect transmission lines so that signals in the inner conductor radiate electromagnetic fields outwardly from the line as the electrical signals are being transmitted down the line. The electrical magnetic fields radiating from the line can be picked up by mobile receivers located remotely, but in the vicinity, of the transmission line. Furthermore, components can be connected directly to the radiating transmission line to modify the signal, such as amplify it, branch the signal to more than one line, or receive and send communication signals such as through radio phones and other electrical components. Radiating transmission line communication systems may also transmit data and/or video signals as disclosed, for instance, in U.S.
Patent No. 5,697,067 to Graham et al. and U.S. Patent No. 7,616,768 to Waye assigned to the same assignee as the present application.
Radiating transmission lines can take on several different forms. One form comprises an open braid coaxial cable. Other forms comprise coaxial cables having cylindrical outer sheaths with longitudinal slits to permit radiation.
Radiating transmission lines are commonly used in environments where electromagnetic waves, such as radio frequency waves, do not propagate well.
This type of

- 2 -environment exists, for example, in underground mine shafts or other types of tunnels. For example, a worker in a mine shaft using a remote mobile communication unit, such as a mobile radio or walkie-talkie, cannot communicate to other workers who also have remote mobile communication units because the radio waves cannot propagate long distances down a mine shaft. However, if all of the workers are near a radiating transmission line, the radio waves from the first worker's remote mobile communication unit could be received by the transmission line, transmitted by the radiating transmission line to the base station, modified, and then transmitted back into the mine and radiated near the remote mobile communication units of other workers. In this way, communication in a mine shaft or other environment where radio frequency waves do not propagate well can be effected.
In the past, several different types of communication systems utilizing radiating transmission lines have been used. However, a common difficulty with most of the prior art communication systems is that it has been difficult to gauge and control the amplification of the signals being transmitted along the radiating transmission line. In particular, because the radiating transmission line is radiating electromagnetic energy, the signals have a much higher degree of loss than other types of transmission lines. It is therefore necessary to control the gain of each of the amplification units. In addition to automatic gain control (AGC) of the amplification units, it is also generally necessary to have automatic slope control (ASC) so as to properly amplify communication signals across a predetermined bandwidth.
In the prior art, to accommodate the control of the communication signals going to and from the base station, pilot signals have been used. The downstream pilot signals had been selected at different frequencies to propagate downstream from the first end of the radiating transmission line, such as into a mine or tunnel, and upstream pilot signals, at different frequencies, to propagate upstream towards the first end of the radiating transmission line. In this way, the upstream pilot signals have been used in the prior art systems to determine the gain required for the signals travelling in the upstream direction by detecting the actual loss of the upstream pilot signal along the length of the radiating transmission line immediately downstream of the amplification unit. In other words, the

- 3 -upstream pilot signals are used in the prior art system to gauge the loss that had occurred over a section of the transmission line immediately downstream to the upstream communication signal travelling in the same direction as the upstream pilot signal, and, then amplify the upstream pilot signal and the upstream communication signal to compensate for the detected actual losses that occurred to the upstream pilot signal.
Similarly, the gain required in the downstream direction has been determined by detecting a corresponding downstream pilot signal along the length of the radiating transmission line immediately upstream of the amplification unit and compensate for the actual loss.
Further wore, having several pilot signals, whether in the upstream or downstream, assists in automatic slope control. This is particularly important in cases where the bandwidth can be 10 MHz up to 40 MHz because the longitudinal loss in a cable is generally higher at higher frequencies than at lower frequencies in the bandwidth.
However, difficulties arise with the prior art systems utilizing this type of upstream pilot signals and downstream pilot signals. In particular, pilot signals travelling upstream towards the first end of the radiating transmission cable may be superimposed if there is a branch. In other words, if the radiating transmission line has been branched out at different points, such as by using branching units, the upstream pilot signal from different ends of the radiating transmission line may be superimposed at the branching points, thereby losing their reference nature and no longer being useful to calibrate the loss in the next length of the radiating transmission line.
Other difficulties also arise with closed loop control systems. These difficulties may include stability problems where overshooting and ringing phenomenon are evident in cascaded amplifier systems. Furthermore, closed loop control systems are associated with constant gain settling time problems. This arises, in part, due to the fact that the time required for the gain of the amplifiers in the system to reach a state output level are not generally constant and the closed loop circuit is affected by the tolerances of electronic components that vary from one amplifier to another. Closed loop control systems are also sensitive to this type of signal modulation which are common in radiating transmission line cables.

- 4 -Accordingly, there is a need in the art to overcome the disadvantages of the prior art systems. In particular, there is a need in the art to provide an improved system and method to control amplifier gain and slope control.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to at least partially overcome some of the disadvantages of the prior art. Also, it is an object of this invention to provide an improved type of system and method to provide automatic gain control with a radiating transmission line.
Accordingly, in one of its aspects, this invention resides in a radio frequency communication system for communicating signals, said system comprising: a radiating transmission line having a first end; a base station coupled to the first end, said base station comprising a base transmitter for transmitting downstream communication signals in a downstream direction away from the first end at a downstream frequency band, and, a base receiver for receiving upstream communication signals in an upstream direction towards the first end at an upstream frequency band, different from the downstream frequency band, said base station further comprising a pilot generator for generating a first downstream pilot signal at a first downstream pilot frequency (fpL) and a second downstream pilot signal at a second downstream pilot frequency (fpH) different from the first downstream pilot frequency (fpL) and transmitting the pilot signals in the downstream direction away from the first end of the radiating transmission line; at least one hi-directional amplification unit coupled to said transmission line for amplifying the downstream communication signal in the downstream direction and amplifying the upstream communication signal in the upstream direction, wherein each hi-directional amplification unit comprises:
(i) a downstream pilot detector for detecting the first and second downstream pilot signals and measuring losses (Lõ,fpL) and (L,õfpn) of the downstream pilot signals over the upstream section (n) of the radiating transmission line immediately upstream of the amplification unit; and (ii) an upstream loss predicting unit for predicting an anticipated loss of the upstream communication signal for the upstream section (n) based on measured losses (La,

- 5 -fn) and (1-,,,fpu) of the first and second downstream pilot signals transmitted over the upstream section (n); and wherein the bi-directional amplification unit amplifies the upstream communication signal in the upstream direction to compensate for the anticipated loss of the upstream communication signal over in the upstream section.
In a further aspect, the present invention resides in an amplification unit for amplifying an upstream communication signal at an upstream frequency band in an upstream direction towards a first end of a radiating transmission line connected to a base station, said communication unit comprising: (a) an upstream connection unit for connecting to a section (n) of the radiating transmission line immediately upstream of the amplification unit; (b) an amplifier for amplifying the upstream communication signal in the upstream direction for transmission on the upstream section of the radiating transmission line connected to the upstream connection; (c) a downstream pilot detector for detecting at least a first downstream pilot signal at a first downstream pilot frequencyfn and a second downstream pilot signal at a second downstream pilot frequencyfm different from the first downstream pilot signalfn, entering from the upstream section (n) of the radiating transmission line connected to the upstream connection and measuring losses (La, fpi.) and (1_,,,fp H) of the first and second downstram pilot signals over the upstream section (n); (d) an upstream loss predicting unit for predicting an anticipated loss of the upstream communication signal in the upstream direction based on the measured losses La, In and 1-,,,,fpu of the downstream pilot signals; and (e) wherein the amplification unit amplifies the upstream communication signal to compensate for the anticipated loss of the upstream communication signal and transmits the amplified upstream communication signal through the upstream connection to the upstream length of the radiating transmission line.
In a still further aspect, the present invention resides a method for amplifying an upstream communication signal at an upstream frequency band in an upstream direction towards a first end of a radiating transmission line, said method comprising:
(a) receiving, at an amplification unit, at least a first downstream pilot signal at a first downstream pilot frequencyfpi and a second downstream pilot signal at a second downstream pilot frequency fn different from the first downstream pilot frequencyfn; (b) predicting an anticipated

- 6 -loss of the upstream communication signal in the upstream direction based on the measured losses L,,fpL and Lnfpfi of the downstream pilot signals; and (c) amplifying the upstream communication signal to compensate for the anticipated loss of the upstream communication signal over the upstream section of the radiating transmission line.
Various embodiments of the present invention have one or more advantages. The present invention provides for the prediction of system losses based on predefined and measured variables which do not vary greatly over time. By predicting transmission losses, the amplification units in the system will be able to predict the losses before they occur and adjust gain accordingly.
A further advantage of certain embodiments of the present invention is that the system performance may be optimized. In other words, the adjusted gain control will facilitate reliable and stable operating conditions for the overall system.
The amplifiers in the communication system will be better controlled by implementing automatic gain control and automatic slope control to operate within their linear range of amplifications.
System instability and AGC time settling issues can also be contained.
A further advantage of certain embodiments of the present invention relates to ease of system installation. Because the system of the present invention does not have an upstream pilot signal, but rather predicts the upstream losses based on the downstream pilot signal, this can reduce the complexity of the system alignments. For instance, because there are no upstream pilot signals, in the system of the present invention, there is no concern that the upstream pilot signal from different ends of a branch may be superimposed. This can save time during installation of the system in part because the amplifiers in the system are automatically adjusting their gains and slopes.
This approach also decreases the demand on highly trained technicians and special alignment tools during installation, thereby reducing time and cost for system implementation, installation and deployment.
A further advantage of certain embodiments of the present invention are that the system can be expandable and flexible. Because of the nature of the automatic compensation for upstream cable losses, automatic compensations due to temperature

- 7 -variations or cable layout changes, facilitate flexibilities and expandabilities in ever growing under ground environments, such as underground mines.
Further aspects of the invention will become apparent upon reading the following detailed description and drawings, which illustrate the invention and preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, which illustrate embodiments of the invention:
Figure 1 is a symbolic representation of a radiating transmission line communication system according to one embodiment of the present invention.
Figure 2 is a graphical representation of the system reference points, downstream communication bands, upstream communication bands and preferred pilot frequencies.
Figure 3 is a block diagram of an amplification unit according to one embodiment of the present invention.
Figure 4 is a flowchart illustrating steps in the method according to one embodiment of the present invention.
Figure 5 is a representation of a radiating line longitudinal loss chart for a particular radiating transmission line which may be used in association with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the invention and its advantages can be understood by referring to the present drawings. In the present drawings, like numerals are used for like and corresponding parts of the accompanying drawings.
As shown in Figure 1, one embodiment of the present invention relates to a radio frequency communication system, as shown generally by reference numeral 10.
The communication system 10 comprises a radiating transmission line 12 having several segments shown generally by variable n, used for communicating downstream and upstream communication signals, shown generally by CSd and CS,õ respectively.
The communication system 10 comprises a base station 24 which is electrically connected to

- 8 -the first end 1 of the transmission line. In a preferred embodiment, the base station 24 comprises an rf combiner 11, a base receiver 26 and base transmitter 28 which together receive the upstream communication signal CSõ and re-transmit the downstream communication signal CSd.
For ease of reference, the communication signals CS travelling away from the first end 1 of the transmission line are referred to as downstream communication signals CSd and the communication signals CS travelling towards the first end 1 of the transmission line 12 are referred to as upstream communication signals CS,. In one embodiment, the base receiver 26 receives the upstream communication signals CS, and the base transmitter 28 re-transmits the information contained in the upstream signal CSõ as the downstream communication signal CSd. In this way, the base receiver 26 and transmitter 28 can act as voice and data repeaters to repeat the infoimation contained in the upstream communication signal CS, in the downstream communication signal CSd. In addition, while not shown, the base station 24 may be connected to radio and/or computers including the Internet, such that data or voice information contained in the upstream data communication signal CSõ may not be re-transmitted into the first end 1 of the transmission line 12, but rather could be used externally from the system 10.
Likewise, data, voice and other information and signals external from the system 10 can be received at the base station 24 and transmitted into the first end 1 of the transmission line 12 base receiver as a downstream communication signal CSd. In this way, the base station 24 can act as a headend for the system 10.
Generally, the base receiver will receive the upstream communication signal CSõ in an upstream frequency band and then the base transmitter 28 may transmit the downstream communication signals CSd in a downstream frequency band which is different from the upstream frequency bandThis is done in order to avoid hamionics and other interference between the communication signals CSõ, CSd.
The radio frequency communication system 10 also comprises a number of amplifiers, as shown generally by the symbols "Amp 01, Amp 02, etc.". Between each amplifier is a separate section n of the transmission line 12. The amplifiers AMP are

- 9 -preferably hi-directional amplifiers and amplify the upstream communication signal CS, in the upstream direction towards the first end 1 of the transmission line 12 connected to the base station 24 and the downstream communication signal CSd in the downstream direction away from the first end 1 of the transmission line 12 connected to the base station 24. The system 10 may also comprise branches 31 which provide a branch from the radiating transmission line 12. The branch 31 will also lead away from the first end 1 of the transmission line. In this way, the downstream communication signal CSd will travel down the transmission line 12 as well as the branches 31 of the transmission line 12. Similarly, the upstream communication signal CS u will travel upstream along the branches towards the first end 1 of the transmission line 12. The system 10 also preferably comprises several portable radios 32 or other types of mobile communication units (not shown). In this way, radio waves being radiated from the radiating transmission line 12 may be received and sent from a remotely located mobile communication unit, such as the portable radio 32, located near the transmission line 12. This is disclosed, for instance, in U.S. Patent No. 5,692,067 to Graham and U.S. Patent No. 7,616,968 B2 to Waye.
In a preferred embodiment, the upstream communication signal CS u will be separated into two upstream data bands; one for the upstream data M=1 and the other for the upstream voice M=3. Similarly, the downstream communication signal CSd will be separated into two downstream data bands; one for the downstream data m=4 and the other for the downstream voice m=2. The following is a table showing the four bands m (two in the upstream direction and two in the downstream direction) for the communication signals CSd and CS u according to one preferred embodiment of the invention:
Band No. Band Name Frequency, MHz.
m=1 Upstream Data 5-42 MHz m=2 Downstream Voice 155-158 MHz m=3 Upstream Voice 172-175 MHz m=4 Downstream Data 220-232 MHz Table 1, Preferred Embodiment System Frequency Plan

- 10 -The base station 24 also preferably comprises a pilot generator 30 to general pilot signals P. The pilot generator 30 generates at least a first downstream pilot signal PSL at a first frequencyfn and a second downstream pilot signal PSH at a second downstream pilot frequeneyfm, different from the first downstream pilot signalfn. In a further preferred embodiment, the pilot generator also generates a third downstream pilot signal PSM at a third frequeneyfpm.
In one preferred embodiment, the above downstream pilot frequenciesfi,L,fpm and fill also represent the preferred reference frequencies for the downstream communication signal CSd in bands m=2 and m=4. In this way, these downstream pilot frequencies can be used to determine the loss of the downstream communication signal CSd and this loss can be used to deteithine the gain and slope that should be used for the downstream communication signals CSd as is known in the art.
Accordingly, in one preferred embodiment, the frequencies of the reference pilot signal will be as follows:
Pilot Frequency (MHz) fpt 157.325 /PM 219.5 232.5 Table 2, Pilot Frequencies and, in a preferred embodiment, downstream band reference point frequency As indicated in Tables 1 and 2, these downstream pilot signals PL, PM and PH
fall within bands m=2 and m=4.
With respect to the upstream communication signals CS, in a preferred embodiment, the upstream reference point frequencies may be as follows:

- 11 -Reference Points Frequency (MHz) _ fi 5.00 f2 42.00 .f3 172.325 Table 3, Upstream Bands Reference Points-Frequencies These frequencies are preferred reference points in cases where the upstream communication signals CSu have the upstream communication bands m=1, m=3, shown in Table 1 above. For convenience, the reference frequencies and the pilot frequencies_ii,i, fpm andfpm for this preferred embodiment are graphically shown in Figure 6.
It has been appreciated that the system losses, which may be represented by reference symbol L, for each section n of the transmission line 12 generally consist of two components. The first component may be called cable longitudinal loss CL, which is mainly due to the longitudinal losses of the section n of the radiating transmission line 12.
Furthermore, the cable longitudinal loss CL is generally a function of the length of the section n of the transmission line 12 and also varies with the frequency of the signal. It has also been appreciated that the second component of the system loss L is not a frequency dependent component and is mainly caused by insertion losses with miscellaneous active and passive units installed in the system 10 and specifically along the section n of the transmission line 12. This second component of the system losses L may be called insertion losses (IL). The insertion losses of these sections n are typically of a flat radio frequency response where the attenuations are almost the same over the entire frequency spectrum of these sections n of the radiating transmission line 12. An example of these miscellaneous active and passive units which cause insertion loss IL may include branch units (such as power dividers or splitters) as well as cable splice boxes for joining two sections of cables together and other types of non-frequency dependent factors. In this way, the two types of losses, namely the frequency specific cable longitudinal loss CL and the non-frequency specific insertion loss IL may be detei ________ mined for each section n of the a transmission line 12 to determine the total loss and therefore the accurate gain

- 12 -compensation for each amplifier in the system for the corresponding frequency band M=1, M=2, M=3 and M=4.
For ease of reference, the system losses referred to above in each cable section n can be represented by the following equation:
= CLnrn+ ILõ (1) where, Lndõ represents the total system loss in one section n of the cable 12 at frequency band m.
CLõ,õ, represents the longitudinal cable loss in one section n of the cable 12. These losses are a function of the cable section n and the frequency f, for each frequency band m.
These losses are generally measured in dB.
IL, represents the total insertion loss of units installed on the section n of the cable 12. These insertion loss IL losses are characteristics of the particular system components measured in dB. The value of the insertion loss of a particular unit is approximately the same for the entire frequency spectrum of the unit's operation (non-frequency dependent component). For example, the insertion loss of a branch unit 31 is approximately 3.5 dB
for entire frequency span (5-232 MHz).
n identifies the cable section n of the radiating transmission line 12 in the system 10 as illustrated, for example, in Fig. 1.
m identifies the band number of the communication signal CS of the system 10 as illustrated in Fig. 6 and shown in Table 1, above, in one preferred embodiment.
Accordingly, in a preferred embodiment, the three pilot signals PL, PH and PM
will be generated at the pilot generator 30 at the base station 24. The pilot signals PL, PH and PM as indicated above, preferably, are selected to be within the downstream voice and data bands as also illustrated in Fig. 6. In this way, the low pilot PL will propagate within the downstream voice band m=2 at frequency,fpL, the mid-point pilot PM will propagate at the lower end of the downstream data band m=4 at frequencyfpm and the high-pilot PH will propagate at the upper end of the downstream data band at frequencyfm, according to one preferred embodiment. In this way, the downstream pilots PL, PM, PH, may be used to determine the gain and slope of the downstream communication signals CSd as is known in

- 13 -the art.
As is also known in the art, the amplitude of the pilots PF, PM and PH will be set by the pilot generator 30 at the system headend 24 to the reference power levels, PL0, PM, and Pflo, respectively, when transmitted. Also, after each amplification unit AMP, the pilot signals PL, PM and PH will again be re-amplified or re-set to the original reference same levels PL,õ PMõ and PH0 in order to permit each subsequent amplifier AMP
in the system 10 to be able to detect the losses of the pilot signals P from the original power level PL0, PM0 and PHo. It is understood that these original power levels, PL0, PK, and PH() will be set at the time of manufacture and/or updated whenever the system 10 is re-set.
According to one preferred embodiment of the invention, at least two downstream pilot signals PL and PH are used to predict the anticipated loss of the upstream communication signal CSõ and the upstream cable section n over which the downstream communication signal CSd and the downstream pilots PL and PH have been transmitted.
In one preferred embodiment, only two of the three reference pilot signals are required to predict the gain in the upstream direction CS,. For ease of explanation, the lower pilot signal PL and the higher pilot signal PH will be used to determine the gain for the upstream signal CSu, but it is understood that any other downstream pilot signals at any two particular frequencies could be used.
As indicated above, in the case where the lower pilot signal PL and the higher pilot signal PH also correspond to the downstream frequency band for the downstream communication signals CSd, the losses of the downstream pilots PL and PH will be equivalent to the losses for the reference frequencies for the downstream band of the downstream communication signal CSd, namely m=2 and m=4, respectively.
Therefore, in this preferred embodiment, the losses for the pilot signals PL and PH, will also be equivalent to the cable losses for the downstream bands m=2 and m=4, and PL
and PH will be interchangeable with m=2 and m=4 in this particular preferred embodiment.
Therefore, the losses of the low pilot PL and high pilot PH will basically be the differences between the original power levels for these pilots PLõ and PH,, at the headend and the measured levels of these pilots when they are detected and measured at each of the

- 14 -amplification units AMP. Each amplifier will also re-amplify the pilot signals PL and PH
to the original levels PLõ and PT-I0 for re-transmission down the next section n+1 of the transmission line 12.
In this preferred embodiment, the system losses L of the low pilot PL at frequency ,fiL, shall also be considered the system losses L for the downstream voice band m=2 and may be represented as follows:
= L0,2 = PLO-PLõ (2) Similarly, the system losses for the high pilot frequency PH at frequencyfm, which in this preferred embodiment also represents the reference frequency for the downstream data m=4, may be represented as:
L0A-1= 4.4 = PHo PH, (3) In this way, the total system losses L of the first cable section have been measured for the low pilot frequencyfn and the high powered frequeneyfm, which, in this preferred embodiment, also corresponds to the loss, and therefore the gain required, for the downstream voice and data bands m=2, 4. However, the general value of CL,,m for different frequencies and the insertion loss ILn have not yet been determined.
Re-writing equation (1) for the total system loss of any cable section n in the downstream direction for bands m=2 and m=4, which in this preferred embodiment also correspond to the frequencies of the low frequency pilot PL and the high frequency pilot PH, we have the following:
CLn>fPL + IL = L,õPL = L,2 = CL02 + IL,, (4) wherefn=M=2 for this preferred embodiment CLn,fpli + IL = LnJH = Lro = CLI,4 + IL, (5) wherefpL=M=4 for this preferred embodiment At this point, it is advantageous to define the relationship between the longitudinal losses of the radiating transmission cable 12 at various frequencies including the pilot frequenciesfn,fpH, which in this preferred embodiment corresponds to the downstream frequency bands m=2 and m=4. This relationship can be used to relate the system losses Lõ, PL of the low pilot signal PL in terms of the system losses Ln,py of the high frequency

- 15 -pilot PH and vice versa. For ease of reference, this is identified below by the downstream low pilot to high pilot cable loss ratio RD defined as follows:
RD = Cable Loss (frt (6a) Cable Loss @fp.H
As discussed above, in the preferred embodiment where the frequenciesfn and,fPn correspond to the downstream bands m=2, m=4, this can be re-written as:
RD = Cable Loss (-&,fpi = CLn,2 (6b) Cable Loss @fpL = CLn,4 The cable loss curve R for different frequencies, including the downstream cable loss ratio RD illustrated in equations (6a) and (6b) above, can be determined for different frequencies and different cables, or can be obtained from the cable manufacturers and is often available in many reference manuals. A sweep test can also be conducted on a particular type of radiating transmission line 12, commonly used in communication systems 10 in order to determine the cable loss curve R and, more particularly, specific cable ratios, such as the downstream cable ratio RD for the low frequency pilot PL and the high frequency pilot PH. The results of one such test are shown in Fig. 5. As is apparent from Fig. 5, the ratio can be generally approximated as a linear slope or curve R.
For this curve R, the downstream ratio RD may be calculated for this preferred embodiment to have the value RD = 0.792. It is understood that any other type of specific downstream ratio values RD can be determined based on the cable loss ratio curve R
illustrated in Fig. 5 and any specific cable loss ratio is deteiniined for specific frequency for each type of radiating transmission cables 12. It is also understood that in general, the curve R does not change with time and is a constant property of the specific radiating transmission 12 and can be determined from the cable frequency response, published by the cable manufacturer or deteiiiiined by a sweep test as indicated above.
It is also generally understood that the curve R does not change appreciably with changes in temperature or other environment or conditions, or, any such environmental changes will affect all frequencies substantially equally, such that the curve R stays substantially the same.

- 16 -Following equation 6 above, we now have related equation:
CL,õfpL = RD*CLn,fpu (7a) which, for this specific embodiment, can be re-written as:
CLn,2 = 0.792 CLn,4 (7b) where PL and PH reflect the reference frequencies for downstream bands m=2, 4 and RD is the downstream ratio for these specific frequencies,fpLJNi and this particular transmission line determined above to be RD = 0.792. It is understood if different types of cables are used, the curve R will change and therefore the value of RD would be adjusted accordingly. Similarly, if different frequencies PL and PH are used, the value for RD will, of course, also change because the frequenciesfpL andfm are different.
Substituting equation 7 into 4 and re-arranging, we have the following equation:
Lfpt = RD*CLnfPu + TL (8a) where for the preferred embodiment discussed above reduces to:
L,,,, = 0.792 CLõ,4 + ILn This can be re-written to solve ILn as follows:
IL n = LJL - RD * CLn.4 (8b) wherefor this preferred embodiment reduces to:
IL,, = 4,2 - 0.792 CL,.4 Substituting equations (8) into (5) and solving for the cable loss CLn,4, we have the following:
GENERAL SPECIFIC TO THIS PREFERRED
EMBODIMENT
L,,,fpH = + LnfPL - RD*CL,LPH L,4 = CLn,4 + L2-0.792*CL,4 LõIpi = (1 + Lõ,fpL 4,4= 0.208*CLn.4 + 4,2 CLn,PH = PH PL) C4,4 = Ln 4 1-11 (1-RD) (9a) 0.208 (9b) Based on the above derivations (9a) and (9b), the longitudinal cable loss CL
for the higher pilot signal PH has been calculated in terms of the measured losses of the higher

- 17 -pilot signal L,f,pH and the measured losses of the lower pilot signal PL, namely Lõ,fpL.
Using the underlying principle in equation 1, that the total system losses Liõ
will have the frequency component based on the cable loss CL and the non-frequency component based on the insertion IL, the insertion loss IL for section n of transmission cable 12, regardless of the frequency, can be re-written as follows:
IL,, = LõfpH - CLII2ipH = LifPH - - Lii/PL) (10a) wherefor the preferred embodiment reduces to:
IL n =L,4 - CL,4 = Ln,4 In 4 __ L) (10b) 0.208 The insertion loss, IL for the section n of the radiating transmission line 12 will be the same for the downstream communication bands m=2, m=4 and the upstream communication system bands m=1, m=3 because IL, is not frequency specific.
As indicated above, using the measured losses Ln,pH and LPL, the gain for the downstream band m=2 and m=4 can then be deteiinined. Therefore, the gain of these bands in the downstream direction to the next section n + 1 of the transmission line 12 can be found and compensated for in each amplification unit AMP as is known in the art.
Furtheimore, now that the insertion loss IL, for the section n has been determined as well as the cable losses CLfn and CLõ,fini, the anticipated loss of the upstream communication signals CS,, in the upstream bands m = 1,3, can be predicted and the upstream communication signal CS,, being transmitted into the same section n immediately upstream of the amplification unit AMP can then be amplified to adjust and compensate for the anticipated losses that have yet to occur, but have been predicted will occur based on the downstream pilot signal PL,PH.
Specifically, using equation (1) above, the system losses for the upstream communication bands, in this case m=1 and m=3, respectively, may be defined by the following:
= CLõ, + IL,, (12) Ln,3 = CL.3 (13)

- 18 -The insertion loss ILn has already been detelmined above, and, as indicated above, is non-frequency specific and therefore this value in equations (12) and (13) has already been determined.
Using the reference frequenciesfi,f2 andf3 as shown in Fig. 6, the predicted signal losses in the upstream frequency band can be determined. For ease of reference, the following references will be used according to a preferred embodiment:
represents the frequency of a reference point at lower end of the data upstream band. This point is not used in calculating the gain of the upstream data band. However, it is used to calculate the slope as shown below.
f2 represents the frequency of a reference point at an upper end of the data upstream band m=1. This point is used in calculating the gain of the upstream data band m=1. The losses at this frequency represent the losses at the upstream data band, m=1.
This reference point is selected to be the point of maximum losses in this band. Frequencyf2 is also used to calculate the slope in the upstream data band m=1 as will be shown below.
f3 represents the frequency of a reference point within the upstream voice band m=3.
This point is used when calculating the gain of the upstream voice band m=3.
The losses at this frequency represent the losses of the upstream voice band, m=3. The frequency f3 is also used to determine the slope as shown below.
Similar to the downstream cable loss ratio, RD, determined from the curve R
(shown in Fig. 5) to define a relationship between the downstream pilot signals PL and PH, upstream cable loss ratios RU can be determined to define relationships between the cable loss at other frequencies, such as the reference downstream pilot frequenciesfpL,fm and the upstream reference frequenciesfi,f2 andf3 as defined above.
In this particular relationship, the following ratios, RU1, RU2 and RU3 for the cable loss ratios with respect to the low frequency pilotfi>L can be determined from curve R:

- 19 -RU1 = Cable Loss gfn (14a) Cable Loss @fi which for this preferred embodiment where the low pilot frequencyfn is the same as the reference frequency for band m=2:
RU1 = CL,7 (14b) CL,,f;
Similarly, the band ratio RU2 for the cable loss ratio between cable losses at low pilot frequencyfn and the cable losses atf2, may be represented as follows:
RU2= Cable Loss (ii),fpt (15a) Cable Loss @f7 which for this preferred embodiment where the low pilot frequencyfn is the same as the reference frequency for band m=2:
RU, = CLõ (15b) CLõf2 Similarly, for the third frequency RU, the upstream cable loss ratio RU3 between the low pilot frequency JPL and the cable loss atf3 may be represented as:
RU3= Cable Loss (fp.t (16a) Cable Loss @f3 which for this preferred embodiment where the low pilot frequencyfPL is the same as the reference frequency for band m=2:
RU3 =CLn 2 (16b) CL,õf3 Using the preferred embodiment shown in Fig. 5, and the preferred frequenciesfi, f3 andfp1-2 andfm=4 the values RU1, RU2 and RU3 may be determined to be RU1=
4.000, RU2 = 1.927 and RU3 = 0.981.
If frequencyf2 is the reference frequency for the upstream data m=1, then we may substitute CL,,,i into equation (15) and obtain the following:
CL,i = CL11J1 = CLidpi (17a) RU, which, for a preferred embodiment where PL is the same as the reference frequency for band m=2 reduces to:

- 20 -CL,1 = CLI1J ¨ CL (17b) (17b) 1.927 Therefore, the predicted total system losses for the upstream data band m=1 in the section n, which is immediately upstream from the amplifier, can be predicted from equation (12) as follows:
L,,,] =CLJ TL, (18a) which the above values CL, PL and IL, have already been deteimined for the section n immediately upstream from the amplifier AMP, and, for this preferred embodiment, can be reduced to the following:
CL, 2 IL, (18b) 1.927 The total system loss in the upstream voice band represented by L3 can be found using the following:
Ln,3 ¨ CLiztPL (19a) which all of the above values CL,õ PL, RU3 and IL, have been determined as identified above. In this way, the anticipated system loss in section n immediately upstream from the amplifier AMP can be predicted and compensated for by amplifying the upstream communication signal CS,, in the band m=3 by the value L1,3. In this preferred embodiment, this value can be determined as follows:
L,3 ¨ CLõ, ILõ (19b) 0.981 At this point, the components of the system loss have been determined for both upstream bands. The gains of the amplifiers in the upstream bands m=1, m=3 have been determined. The amplifier can then amplify the upstream signals CS, to compensate for this anticipated loss as described more fully below. Accordingly, based on the above, the amplifiers AMP will amplify the upstream signals CS,,, to compensate for the anticipate loss which the upstream signals CS, in bands m=1 and m=3 will experience when the upstream signal CSõ propagates through the upstream section n of the cable 12.

-21 _ In cases where the bands m=1, m=2, m=3 and m=4 have a wide bandwidth, such as more than 10 MHz, the radio frequency response of the cable section n will vary over this bandwidth such that it will have a shape or negative slope, sometimes referred to as a Tilt across the bandwidth m. The longitudinal loss in the cable in the higher frequencies will, of course, be higher than the loss at the lower frequencies which is also illustrated from the curve R as shown in Fig. 5. For example, cable sweep tests have shown that for a cable length of 350 meters, negative slope of approximately 2 dB, were produced within the data downstream band m=4 which, at least in this preferred embodiment, is 12 MHz between 220 - 232 MHz. The upstream data band m=1, which in this preferred embodiment is 5 -42 MHz can have a slope or tilt of 6 dB because it is a bandwidth of about 37 MHz.
In order to measure the slope in the bandwidth, it is preferred that the wider band widths of 10 MHz or wider have two reference pilots, one at the upper end and one at the lower end to be able to accuragely determine the slope T.
As indicated above, based on the curve R and the low pilot PL and high pilot PH, it would be possible to determine losses at any other frequency including the downstream mid-point pilot PM. However, in order to improve the accuracy of the system, and given that the downstream pilots PL, PM, PH are relatively simple to manage because they all travel away from the first end 1 of the radiating transmission line 12, in a preferred embodiment, three downstream pilot signals PL, PM and PH are used. Otherwise, the middle pilot signal PM representing the lower end of the downstream data band m=4, could be predicted using the equations above and the curve R.
To calculate the slope in the downstream data band, the system losses for the pilots PM and PH may be used. The losses added to PH have been calculated in equation (3) above.
The losses for the mid-point pilot PM, when it is used, may be calculated as follows:
LnfpM ¨ PM0 - PMn (20) where PMo is the original level of the pilot PM and PMn is the measured value of PM.
The slope in the downstream data band can then be calculated as follows:

- 22 -T4 = 1-m,4 - LniPM (21) where T4 is the slope for the data downstream band m=-4 in this preferred embodiment and the losses Ln,4 represent the losses of the high frequency pilot signalfpu.
Next, the slope for the upstream data band m=1 may be calculated. This slope may be represented by T1. To calculate the slope Ti, the cable longitudinal losses CLn,f1 and CLõ,f2 at the two references pointsfi andf2 of band m-1, respectfully are required.
From equations 14 and 15 above and using the cable loss ratios RU1 and RU2, the following equation can be derived:
CLJj=CLPL (22a) which for this preferred embodiment is:
CLõ,fi = CL n 2 (22b) 4.999 If the second reference frequencyf2 is considered to be the reference for band m=1, then CL,,f2 is the same as CLõ,i, which was calculated in equation (17) above.
Using this equation, the slope Ti and the upstream data band m=1 can be calculated as follows:
T1 = CLõ,f2 - CLf (23) It is apparent where a comparison from equations (21) and (23) that for the upstream data band m=1, the cable loss values CL,õf2 and CLõ,fi may be used to determine the slope Ti. In contrast, equation 21 the total losses Lõ,fpH - Lnii,m are used because the actual loss Lnym has been measured in this preferred embodiment. However, because the only difference between the total loss L and the cable loss CL is the insertion loss IL, which is non-frequency dependent, the slope T should be substantially the same whether the total loss L is used or the cable loss CL is used.
On this basis, in case only two pilot signals are used, namely PL and PH, then the slope for the downstream data band m=4 may be the following:
T4 = CL,/PH CLniPM
where CLõ,pm may be determined from the curve R and the measured losses L of the low

- 23 -pilot PL and high pilot pH and CLn,fpH has been determined above in equation (9).
Using the above equations, the amplification units AMP in the system 10 can amplify the downstream signals CSd into the next, or downstream, section n+1 of the communication system 10 using the measured losses L in the pilots PL, PH and, if used, PM. The controlled gain for the upstream communication signals CSõ may be predicted using the anticipated loss of the upstream signals CSõ into the upstream section n of the radiating transmission line 12 immediately upstream from the amplification unit AMP
based on the measured losses from the downstream pilot signals PL and PH and, if used, PM transmitted through the upstream section n.
Figure 3 illustrates a block diagram of an amplification unit AMP, identified generally by reference numeral 100, according to one preferred embodiment.
As shown in Figure 3, the amplification unit 100 preferably comprises an upstream connection unit 102 for connecting to an upstream section n of the radiating transmission line 12. It is understood that the upstream connection unit 102 will receive radio frequencies RF representing the downstream communication signals CSd and send RF
frequencies representing the upstream communication signals CS. However, because the connection unit 102 is connected to the section n of the radiating transmission line 12 immediately upstream from the amplification unit 100, this connection unit 102 will be referred to as the upstream communication unit 102 for ease of reference.
Similarly, the amplification unit 100 has a downstream connection unit 104 for connection to the section n+1 of the radiating transmission line 12 that is immediately downstream from the amplification unit 100. The downstream connection unit 104 will receive radio frequency RF signals representing the amplified downstream communication signal CSd and receive radio frequency RF signals representing the upstream communication signal CSii.
As is also illustrated in Figure 3, the downstream connection unit 104 will also transmit the re-amplified pilot signals PL,, and PH,, and where a third signal is used, PM,. It is understood that re-amplified pilot signals will have the same amplitude as the signals that emanated originally from the pilot generator 30 at the base station 24.
Similarly, the upstream connection unit 102 will receive the downstream pilot signals PL and P1-1 and, =
, .

- 24 -where used, PM, which have traveled down the upstream section n of the radiating transmission line 12. It is understood that the pilot signals PL and PH and, where used, PM, will have experienced a loss in transmission over the upstream section n of the radiating transmission line 12. It is also understood that the pilot signals P
would have emanated either from the base station 24 or from another amplification unit 100 and, in either case, would have initially entered into the upstream section n of the radiating transmission line 12 having the same amplitude as when originally generated by the pilot generator 30 in the base station 24.
As is also known in the art, the amplification unit 100 will have various radio frequency combiners, filters, wave guides and other electronics which would be known to a person skilled in the art and are not necessarily represented in the general graphical representation of the amplification unit 100 as shown in Figure 3. However, Figure 3 does illustrate various filters 136 between the internal components of the amplification unit 100 and the connection units 102, 104. As also illustrated in Figure 3, the amplification unit 100 preferably comprises a directional coupler 138 which separates the downstream communication signal CS(.1 from the downstream pilot signals PL, PH and, where used, PM. The pilot signals PL, PM and PH, as shown in Figure 3, pass through further filters 139 and then enter into the respective detectors, namely the low pilot PL
detector 130 PL, the mid-pilot detector 130 PM and the high pilot detector 130 PH. Emanating from each of the detectors 130 is the corresponding measured loss signal LiõfpL, and Lnipli, which is then received by the microcontroller 120.
It is understood that the microcontroller 120 would perform several functions in controlling the amplification unit 100. It is also understood that the amplification unit 100 may have more than one microcontroller 120, but for ease of reference, only one microcontroller 120 is illustrated in Figure 3. Furthermore, the microcontroller 120 in a further embodiment will comprise an insertion loss component 122, a cable loss component 124 and a slope deteimining component 126. It is understood that each of these components 122, 124, 126 could be software or hardware components controlled by, or foiming part of, the microcontroller 120. It is also understood that the components 122,

-25 _ 124 and 126 could be stand alone units and may have a separate microcontroller or processor, such as in cases where the amplification unit 100 has been retrofitted with this hardware. In a preferred embodiment, the microcontroller 120 will have the hardware and software capacity to include the components 122, 124 and 126. Therefore, the microcontroller 120 performs the function of an upstream loss prediction unit.
It is understood that the insertion loss component 122 will receive the measured losses L,õfpl , Lfpm and Lndepi) and determine the various values and, specifically, the insertion loss IL, for each section based on the equation (10) indicated above. It is noted that Figure 1 illustrates the calculated insertion losses ILn for the sections n of this preferred embodiment. The distance D of each section n is also shown in Figure 1. In order to perfoim these calculations, it is understood that the microcontroller 120 of each amplification unit AMP 100 will have been previously programmed with software and/or supplied with hardware to perform the functions indicated by the equations above, including information regarding the curve R illustrated in Figure 5.
Similarly, the cable loss component CL, 124 will perfoim the calculations determined to perform the cable loss for both the downstream signals CSd and the upstream signals CS. It is understood that in the preferred embodiment where the pilot signals PL
and PH also correspond to the reference frequencies for the downstream bands m=2, m=4, the downstream cable loss calculation and downstream insertion loss calculation will simply be a subtraction of the measured values L,õfpL and 1_,,,,fPn from the original values PL0 and PH0 as indicated in equations (2) and (3) above. For the upstream communication signals CSõ, the upstream predicted cable losses 4,1 and L03 will be based on the measured losses of downstream pilots PL and PH as indicated in equations (18) and (19) above.
Similarly, the slope T will be determined for any communication signals CS
that have a bandwidth of greater than 12 MHz and preferably greater than 10 MHz. In this preferred embodiment, as indicated above, the slope T will be calculated for the downstream data band m=1 (Ti) and the upstream data band M=4 (T4). As indicated above, in cases where the system 10 does not have a midpoint downstream pilot PM, the lower end of the cable loss CL at the lower end of the data band M=4 can be determined

- 26 -and the slope T4 calculated from equation (24). In the preferred embodiment, where a downstream midpoint pilot PM is used, the actual measured losses Lii,fpx and Lõ,fpm will be used to determine the slope T4 based on equation (21). For the upstream communication signal CSõ, in this preferred embodiment, the upstream data band m=1 has a bandwidth greater than 10 MHz, such that the slope T1 for bandwidth m=1 would need to be calculated. In this case, as indicated above, the slope T1 for bandwidth m=1 would be calculated based on equation (23).
The results from the components 122, 124 and 126 are then processed and sent to the downstream digital attenuator 140d and downstream slope control 142d in order to shape the downstream communication CSd. The downstream digital attenduator 140d and downstream soap control 142d and amplifier 145 will generally amplify the downstream communication signal CSõ as is currently done and based on the downstream pilot signals PL, PH and, where used, PM.
The controller 120 will also provide results from the components 122, 124 and to the upstream digital attenuator 140u, the upstream slope control 142u and the amplifier 145 to amplify the upstream communication signals CSõ. In this case, however, the upstream communication signal CSõ will be attenuated and the slope will be controlled based on the anticipated loss the upstream communication signal CSõ will experience over the section n of the radiating transmission line 12 immediately upstream from the communication signal 100. Therefore, the gain and slope of the upstream communication signal CS,, will be controlled to compensate for the anticipated loss that the upstream communication signal CS, will experience based on the predicted loss for the upstream communication signal CSõ in bands m=1, m=3 based on the losses measured from the downstream pilot signals PL, PH and, where used, PM.
Once the downstream signals CSd exit the slope control 142d, it will be amplified by amplifiers 145, passed through the filter 136 and exit through the downstream connection 104. Similarly, once the upstream communication signals CS, exits the upstream slope control 142u, it will be amplified by the amplifier 145, passed through the filter 136 and exit though the upstream connection 102 into the upstream section n of the _ 77 _ radiating transmission line 12. It is understood, however, that the downstream communication signals CSd leaving from the amplification unit 100 will have been amplified to compensate for the losses that occurred after the downstream communication signals CSd passed through the upstream section n of the cable 12 and therefore the signal CSd will have an amplitude similar to that which would normally have when it exited from the base transmitter 28 of the base station 24. In contrast, the upstream communication signal CS,, leaving the amplification unit 100 will have been amplified to compensate for the anticipated losses which the upstream communication signal CS,, will experience when it is transmitted through the upstream section n of the radiating transmission line 12, based on the downstream pilots PL, PH and where used PM. In this way, the upstream communication signals CS,, that is received, either by the base receiver 26 if this is the first amplifier in the first communication system 10, or, the next upstream amplification unit 100 in the system 10, will be substantially similar to the unamplified upstream communication signal CS.
Figure 4 is a flow chart illustrating the steps in a method according to one preferred embodiment of the present invention. As illustrated in Figure 4, the flow chart 400 comprises a start section 401 which leads to setting variables 402. The variables include the pilot levels at the head end, namely PLõ, PM0, PH,, as well as the cable loss ratios based on curve R that will be used for the particular frequenciesf,f2 andfi as well as the pilot signalsfpL,fm and, where used,fpm=
In section 404 that data is inputted meaning that the detectors 130 in each amplification unit 100 measure the input levels of the downstream pilots PL, PH and PM
and these values are then stored in microprocessor 120 or memory (not shown).
In section 406, various calculations are made based on the equations 1 to 24 as outlined above. For instance, step 501 calculates the band m=2 system loss based on equation (2). In step 502, the band m=4 system losses are calculated based on equation (4).
Subsequently, in step 503, the band m=4 cable loss is calculated based on equation (9).
Subsequent to that, in step 504, the section insertion loss ILn is calculated based on equation (10). Finally, the band m=2 cable loss can be calculated in step 505 based on equation (7).
In section 407 of the flow chart 400, the upstream band m=1 cable loss is calculated and in step 506 based on equation (14), and the band m=3 cable loss is calculated in step 507 based on equation (16). In step 508, the total system loss for upstream band m=1 is calculated and in step 509 based on equation (18), and, the upstream communication signal CSi, band m=3 total system loss Ln3 is calculated in step 509 based on equation (19).
In section 408, of the flow chart 400, the system gains are then determined for each of the bands m=1, m=2, m=3 and m=4, which are essentially equivalent to the actual measured losses for the downstream communication signal bands m=2, m=4 and the anticipated losses for the upstream communication bands m=1, m=3.
In section 409 of the flow chart 400, the system tilts for the bandwidths greater than MHz are calculated. Specifically, in step 511, the upstream data band cable losses are determined through both reference frequenciesfi andf2 of the upstream data band m=1. In step 512 in cases where the third pilot signal PM is used, the total system loss for Ln,finvi is determined. Finally, in step 513, the upstream and downstream data band tilts T1, Tzt are calculated based on equations (23) and (21), respectively.
In section 410 of the flow chart 400, the microprocessor 120 outputs the variable attenuators adjustment gains GI, G2, G3 and G4 to the downstream digital attenuator 140d and upstream attenuator 140u, respectively. Finally, in step 514, the microprocessor outputs the slopes T1 and T4 to the downstream slope control 142d and upstream slope control 142u at step 152. In section 411 of the flow chart 400, there is a repeat step 516 after a short period of time.
To the extent that a patentee may act as its own lexicographer under applicable law, it is hereby further directed that all words appearing in the claims section, except for the above defined words, shall take on their ordinary, plain and accustomed meanings (as generally evidenced, inter alia, by dictionaries and/or technical lexicons), and shall not be considered to be specially defined in this specification. Notwithstanding this limitation on the inference of "special definitions," the specification may be used to evidence the appropriate, ordinary, plain and accustomed meanings (as generally evidenced, inter alia, by dictionaries and/or technical lexicons), in the situation where a word or term used in the claims has more than one pre-established meaning and the specification is helpful in choosing between the alternatives.
It will be understood that, although various features of the invention have been described with respect to one or another of the embodiments of the invention, the various features and embodiments of the invention may be combined or used in conjunction with other features and embodiments of the invention as described and illustrated herein.
Although this disclosure has described and illustrated certain preferred embodiments of the invention, it is to be understood that the invention is not restricted to these particular embodiments. Rather, the invention includes all embodiments, which are functional, electrical or mechanical equivalents of the specific embodiments and features that have been described and illustrated herein.

Claims (19)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A radio frequency communication system for communicating signals, said system comprising:
a radiating transmission line having a first end;
a base station coupled to the first end, said base station comprising a base transmitter for transmitting downstream communication signals in a downstream direction away from the first end at a downstream frequency band, and, a base receiver for receiving upstream communication signals in an upstream direction towards the first end at an upstream frequency band, different from the downstream frequency band, said base station further comprising a pilot generator for generating a first downstream pilot signal at a first downstream pilot frequency (.function.pL) and a second downstream pilot signal at a second downstream pilot frequency (.function.PH) different from the first downstream pilot frequency (.function.PL) and transmitting the pilot signals in the downstream direction away from the first end of the radiating transmission line;
at least one bi-directional amplification unit coupled to said transmission line for amplifying the downstream communication signal in the downstream direction and amplifying the upstream communication signal in the upstream direction, wherein each bi-directional amplification unit comprises:
(i) a downstream pilot detector for detecting the first and second downstream pilot signals and measuring losses (L n,.function.PL) and (L n, .function.PH) of the downstream pilot signals over the upstream section (n) of the radiating transmission line immediately upstream of the amplification unit; and (ii) an upstream loss predicting unit for predicting an anticipated loss of the upstream communication signal for the upstream section (n) based on measured losses (L n,.function.PL) and (L n,.function.PH) of the first and second downstream pilot signals transmitted over the upstream section (n); and wherein the bi-directional amplification unit amplifies the upstream communication signal in the upstream direction to compensate for the anticipated loss of the upstream communication signal over in the upstream section.

2. The radio frequency communication system as defined in claim 1 wherein at least one of the first and second downstream pilot frequencies are selected to be within the downstream frequency band; and wherein the upstream loss predicting unit determines the anticipated loss at the upstream frequency band based on the determined signal loss of the first and second downstream pilot signals.

3. The radio frequency communication system as defined in claim 2 wherein the at least one of the first and second downstream pilot frequencies which is selected to be within the downstream frequency band is a downstream reference frequency for the downstream frequency band; and wherein the system losses for the downstream frequency band will be calculated based on the actual losses measured by the at least one downstream pilot frequency as follows:
L n,CS (downstream) = P o - P n where n identifies the upstream section of the cable immediately upstream of the amplification unit;
P n identifies the actual loss of the at least one pilot signal; and P o represents the original amplitude of the at least one downstream pilot signal; and wherein the bi-directional amplification unit amplifies the downstream amplification unit to compensate for the actual losses measured by L n,CS
(downstream) over the upstream section.

4. The radio frequency communication system as defined in claim 1 wherein the upstream loss predicting unit comprises a Cable Longitudinal Loss (CL) predicting component to determine cable losses in the upstream section of the radiating transmission line and an Insertion Loss (IL) predicting component to determine component losses in the upstream section of the radiating transmission line.

5. The radio frequency communication system as defined in claim 4 wherein the insertion loss (IL) predicting component determines the loss in the upstream direction based on the following equation:
where IL n is the insertion loss at the section n of the radiating transmission line;
L n,.function.PL is the total measured system loss at the section n for the first pilot frequency;
L n,.function.PH is the total measured system loss at the section n for the second pilot frequency .function.PH; and RD is a downstream ratio of the cable loss of the first pilot frequency .function.PL to the second pilot .function.PH for the radiating transmission line.

6. The radio frequency communication system as defined in claim 5 wherein the cable longitudinal loss (CL) predicting component predicts losses in the upstream section immediately upstream of the amplification unit based on the following equation:
where n identifies the upstream section of the cable immediately upstream from the amplification unit;
.function.PL is the first pilot signal frequency; and RU is a ratio of the cable loss at the first downstream pilot frequency fn to a reference frequency CS (upstream) for a reference frequency for the upstream frequency band for the radiating transmission cable.

7. The radio frequency communication system as defined in claim 6 wherein the predicted upstream communication signal loss L n,CS (upstream) is based on the following equation:
L n,CS (upstream) = CL n,CS (upstream) + IL n.

8. The radio frequency communication system as defined in claim 1 wherein the upstream frequency band is greater than 10 MHz and a slope T n,CS (upstream) for the upstream communication signal is calculated based on the following equation:
T n,CS (upstream) = CL n,CS (upstream at .function.1) - CL n,CS (upstream at .function.2) where CL n, CS (upstream at .function.1) is a cable loss for a reference frequency at a higher end of the upstream frequency band for the section n and CL n,CS (upstream at .function.2) is a cable loss over section n for a second reference frequency .function.2 and at lower end of the upstream frequency band; and wherein CL n, CS (upstream at .function.1) and CL n,CS (upstream at .function.2) are based on measured losses of the downstream pilot signals L n,.function.PL, and L
n,.function.PH and a substantially linear curve R representing cable loss for different frequencies of the radiating transmission line.

9. The radio frequency communication system as defined in claim 8 wherein the upstream communication signals comprise data signals in a first upstream frequency band and voice signals in a second upstream frequency band; and wherein the data signals in the first upstream frequency band have a bandwidth a greater than 10 MHz and the second upstream communication band has a bandwidth less than 10 MHz; and wherein the slope T n,CS (upstream) is calculated for the first upstream frequency band.

10. An amplification unit for amplifying an upstream communication signal at an upstream frequency band in an upstream direction towards a first end of a radiating transmission line connected to a base station, said communication unit comprising:

(a) an upstream connection unit for connecting to a section (n) of the radiating transmission line immediately upstream of the amplification unit;
(b) an amplifier for amplifying the upstream communication signal in the upstream direction for transmission on the upstream section of the radiating transmission line connected to the upstream connection;
(c) a downstream pilot detector for detecting at least a first downstream pilot signal at a first downstream pilot frequency .function.PL and a second downstream pilot signal at a second downstream pilot frequency .function.PH different from the first downstream pilot signal .function.PL, entering from the upstream section (n) of the radiating transmission line connected to the upstream connection and measuring losses (L n, .function.PL) and (L n,.function.PH) of the first and second downstram pilot signals over the upstream section (n);
(d) an upstream loss predicting unit for predicting an anticipated loss of the upstream communication signal in the upstream direction based on the measured losses L
n,.function.PL and L n,.function.PH of the downstream pilot signals; and (e) wherein the amplification unit amplifies the upstream communication signal to compensate for the anticipated loss of the upstream communication signal and transmits the amplified upstream communication signal through the upstream connection to the upstream length of the radiating transmission line.

11. The amplification unit as recited in claim 10 wherein the upstream loss predicting unit further comprises:
a cable longitudinal loss (CL) predicting component for determining cable losses in the upstream section and of the radiating transmission line; and an insertion loss predicting component (IL) for determining component losses in the upstream section of the radiating transmission line.

12. The amplification unit as recited in claim 11 wherein the insertion loss (IL) predicting component determines the loss in the upstream direction based on the following equation:

where ILn is the insertion loss at the section n of the radiating transmission line;
Ln,.function.PL is the total measured system loss at the section n for the first pilot frequency;
and .function.PL and Ln,.function.PH is the total measured system loss at the section n for the second pilot frequency .function.PH;
RD is a downstream ratio of the cable loss of the first pilot frequency .function.PL to the second pilot .function.PH for the radiating transmission line.

13. The amplification unit as recited in claim 12 wherein the cable longitudinal loss (CL) predicting component predicts losses in the upstream section immediately upstream of the amplification unit based on the following equation:
where n identifies the upstream section of the cable immediately upstream from the amplification unit;
.function.PL is the first pilot signal frequency; and where RU is a ratio of the cable loss at the first downstream pilot frequency .function.PL to a reference frequency CS (upstream) for a reference frequency for the upstream frequency band for the radiating transmission cable.

14. The amplification unit as recited in claim 13 wherein the upstream loss predicting unit further comprises an upstream slope T predicting component for predicting a slope TnCS (upstream) of the upstream bandwidth for the upstream communication signal calculator based on the following equation:
Tn,CS (upstream) = CLn,CS (upstream at .function.1) - CLn,CS (upstream at .function.2) where CLn, CS (upstream at .function.1) is the cable loss for a reference frequency at a higher end of the upstream frequency band for the section n and CLn,CS
(upstream at .function.2) is the cable loss over section n for a second reference frequency f2 and at lower end of the upstream frequency band; and wherein CL n, CS (upstream at f1) and CL n,CS (upstream at f2) are based on measured losses of the downstream pilot signals Ln,f pL and L n, f PH and a substantially linear curve R representing cable loss for different frequencies of the radiating transmission line.

15. The amplification unit as recited in claim 10 wherein the amplification unit is a bi-directional amplification unit and amplifies downstream communication signals at a downstream frequency band, different from the upstream frequency band, said amplification unit comprising:
a downstream connection unit for connecting to a downstream section (n + 1) of the radiating transmission line immediately downstream of the amplification unit;
(g) a downstream amplifier for amplifying the downstream communication signals in the downstream direction at the downstream communication band for transmission on the downstream section of the radiating transmission line connected to the downstream connection;
(h) a downstream loss measuring unit for determining the loss of the downstream communication signals from the measured losses of at least one of the downstream pilot signals PL, PH based on the equation:
L n,CS (downstream) = P o - P n where n identifies the upstream section of the cable immediately upstream of the amplification unit;
P n identifies the actual loss of the at least one pilot signal; and P o represents the original amplitude of the at least one downstream pilot signal.

16. A method for amplifying an upstream communication signal at an upstream frequency band in an upstream direction towards a first end of a radiating transmission line, said method comprising:
(a) receiving, at an amplification unit, at least a first downstream pilot signal at a first downstream pilot frequency f PL and a second downstream pilot signal at a second downstream pilot frequency f PH different from the first downstream pilot frequency f PL;
(b) predicting an anticipated loss of the upstream communication signal in the upstream direction based on the measured losses L n, f PL and L n f PH of the downstream pilot signals; and (c) amplifying the upstream communication signal to compensate for the anticipated loss of the upstream communication signal over the upstream section of the radiating transmission line.

17. The method of claim 16 further comprising an initial step of:
setting variables corresponding to the original values of the downstream pilot signals PL o and PH o and setting values corresponding to cable loss ratios RD
and RU based on a curve R of the radiating transmission line.

18. The method of claim 16 wherein the step of predicting the anticipated loss of the upstream communication signal comprises:
(b1) predicting the insertion losses IL for components installed on the upstream section of the radiating transmission line based on the following equation:
where IL n is the insertion loss at the section n of the radiating transmission line;
L n,f PL is the total measured system loss at the section n for the first pilot frequency;
L n,f PH is the total measured system loss at the section (n) for the second pilot frequency f PH; and where RD is a downstream ratio of the cable loss of the first pilot frequency f PL to the second pilot f PH for the radiating transmission line.

19. The method of claim 18 wherein the step of predicting the anticipated loss of the upstream communication signal further comprises:

(b2) predicting the cable loss CL for cable losses in the upstream section of the radiating transmission line based on the following equation:
where n identifies the upstream section of the cable immediately upstream from the amplification unit;
.function.PL is the first pilot signal frequency; and RU is a ratio of the cable loss at the first downstream pilot frequency .function.PL to a reference frequency CS (upstream) for the upstream frequency band for the radiating transmission cable.