MXPA00003796A - Intelligent packet retransmission scheme - Google Patents

Abstract

To achieve an improved utilization of a radio link channel in a wireless packet oriented transmission system data packets are transmitted between a transmission apparatus (10) and a mobile unit (14), respectively. Then it is determined whether a data packet transmission between the transmission apparatus (10) and the mobile unit (14) has been carried out successfully. Here, a transmission channel (16) is reassigned to another mobile unit (14) in a case that it is determined that the transmission of the data packet was not successful and further a retransmission of a data packet is estimated to be not successful.

Description

INTELLIGENT PACKET RETRANSMISSION SCHEME FIELD OF THE INVENTION _ This invention relates to a transmission apparatus for a wireless communication system in accordance with the preamble of claim 1. Furthermore, this invention relates to a mobile unit for a system of wireless communication according to the preamble of claim 21. Further, the present invention relates to a method for transmitting data packets in a wireless communication system in accordance with the preamble of claim 28. BACKGROUND OF THE INVENTION ~~ ~ Said transmission apparatus, mobile unit and method for transmitting data packets in a wireless communication system is known from EP 0 794 631 A2 which describes an error control method and an apparatus for wireless data communication. Particularly, EP 0 794 631 A2 discloses an error control method for wireless data transmission in a digital mobile communication system that includes a step of obtaining, during data communication, a statistical information including error information of transmission on a receiving side, further a step of determining an error control strategy and / or a value of at least one parameter of the error control strategy that are optimal for transmission path conditions at this time, based on in the statistical information obtained, and a step of determining an error control strategy and / or a value of at least one parameter of the error control strategy that are optimal for transmission path conditions at this time based on the Statistical information obtained. Furthermore, in document US-A-4, 939, 731 there is described a data transmission system comprising several radio stations. Each radio station includes a transceiver with an associated encoding / decoding device for transmitting / receiving data. Data signals are transmitted as data packets in which they include one or more data blocks encoded with an error correction code. Each radio station is automatically arranged to issue a request to repeat a data packet in which it receives errors that can not be corrected. If the frequency of errors in the received data packets is greater than a certain amount during a predetermined interval of data transmission, the system is automatically arranged to reduce the data transmission speed in each data packet and / or to change the channel frequency. In wireless communication systems, radio waves propagate in space as EM electromagnetic waves. Signal energy exists in the form of electrical and magnetic fields H. Both electric and magnetic fields vary sinusoidally over time. The two fields exist together since a change in the electric field generates a magnetic field and a change in the magnetic field generates an electric field. Thus, there is a continuous flow of energy from one field to the other. The radio waves arrive at a mobile station in a wireless communication system from different directions with different time delays. They are combined through addition of vector in the receiver antenna in order to provide a resultant signal with a large or small amplitude depending on whether the combined incoming waves lie between them or cancel each other. As a result, a receiver in the indication can experience a signal strength with a difference of several tens of dB compared to a similar receiver located only a short distance away. As mobile reception moves from one location to the other, the phase relationship between the various incoming waves also changes. Thus, there are substantial phase amplitude fluctuations and the signal is subject to fading. It is also observed that if there is a relative movement of the mobile reception, there is also a Doppler shift in the received signal. In the case of a mobile radio, fading and Doppler shift occur as a result of receiver movement through a field that varies in space. In addition, it also results from the movement of dispersers of radio waves such as: cars, trucks, vegetation. Thus, the effect of multipath propagation is the production of a received signal with an amplitude that varies substantially with location. In addition, in UHF and higher frequencies, the movement of the dispersers also causes fading even if the mobile device is not moving. Figure 19 illustrates the global fading characteristics of a mobile radio signal. Here, the rapid fluctuation caused by the local multiple path is known as fast fading or excessive Rayleigh fading. Figure 20 shows the basic mechanism that serves as the basis for this phenomenon of fading. As mobile telephony becomes increasingly popular, the density of subscribers in particular in cities increases continuously. Thus, employing a mobile station in such an environment causes the amplitude and phase fluctuation explained above. As shown in Figure 20, the radio signals arrive from different directions in such a way that the signal follows more than one path from the transmitting antenna T to the receiving antenna R. The signal is not received directly from the antenna transmitter, but also from other directions where bounced, such as buildings Bl to B6. Globally the signal (s) arrive at the MS station through several reflections against these buildings Bl to B6. This means that the received signal is the sum of many identical signals that differ as for example, only in phase and to some extent also in amplitude. This eventually means that the sum of the identical signal is very close to zero, and that the strength of the signal is also very close, the worst case of falling by fading. ~~ As shown in Figure 21, another type of fading results from shading effects, such as the use of the mobile station in an environment with obstacles. In accordance with Figure 21, hills H and buildings B may exist between the transmitting antenna T and the receiving antenna R of the mobile station MS in such a manner that the received signal loses strength. The fading caused by shading effects is known as log-nor fading since the logarithm of the signal strength takes the form of a normal distribution around a certain average value. Typically, the distance between two minima or caldos per fading is approximately 10 to 20 meters. A fade effect strongly related to log-normal fading is what is known as the Rice fading. In particular, in systems that base a free line between the transmitting antenna T and the receiving antenna R, this effect occurs when the line is disturbed. In this case, the strength of the signal will decrease dramatically when the distance line is blocked and the receiving antenna receives only reflected signals. Furthermore, according to the figure the third phenomenon of signal strength reduction of its distance is the propagation loss that occurs when the received signals become increasingly weak due to an increasing distance between the transmitting antenna T and the antenna receiver R. The higher the frequency, the higher the attenuation. Finally, as shown in Figure 22, the transmission of data packets leads to the phenomenon of time distortion. The time dispersion, too, has its origin in reflections, but, unlike multipath fading, the reflected signals come from objects remote from the receiving antenna R, that is, in the order of kilometers. The dispersion of time leads to interferences between symbols where consecutive symbols interfere with each other in such a way that it is difficult on the receiving side to decide which current symbol has been detected. Since the reflected signals come from distant objects, instead of a single transmitted pulse, several different pulses can be received in accordance with the long distances and the associated delay times. As for example, in the case of Sends of the sequence 1.0 from the transmitting antenna as shown in Figure 22, the reflected signals take exactly one time of a 1 bit after the direct signal, the receiving antenna will detect a value of 1 from the reflected signal at the same time that it detects a value of or of the direct wave in such a way that both symbols present interferences. As presented above, all wireless systems have to handle the unreliable nature of the radio link. The loss of single bits or a row of bits is normal in the case of a radio link. Likewise, the loss of information is caused by the variation of the strength of the signal, which makes communication impossible if it falls below a certain threshold. To overcome the problem of variation in signal strength, several mechanisms are employed at different protocol levels. These mechanisms are for example, forward error correction, power control, frequency hopping and retransmission. In accordance with the present invention, the case of retransmission is particularly considered when losing data and improving the underlying schemes. Here you can add redundancy to the transmit data which allows the detection of transmission errors on the receiving side. The amount of bridging is determined in such a way that the detection of errors in the bits can be carried out, but not its correction. In the case of detection by the receiver of a bit error of this type, it requires the transmission of the data again. This is usually achieved through a negative acknowledgment sent to the issuer. In addition, an acknowledgment must be sent for each data transmitted on the radio link that is not reliable. These acknowledgments can be grouped together and accused of recording either several data together or of each data separately. The appropriate form of sending an acknowledgment of receipt is decided based on the amount of additional signaling and delay information experienced by the end user that must be taken into account. Once the acknowledgment is specified in the retransmission scheme, each data loss is handled in the same way regardless of the type of disturbance. Even worse, data that does not cross a certain threshold is not treated since the complete connection is lost in the case of an excessive duration of the disturbance. COMPENDIUM OF THE INVENTION Taking into account the aforementioned, the object of the present invention is to achieve an improved use of a radio link channel to which several users have access in a wireless packet-oriented transmission system. In accordance with an aspect of the present dimension, this object is achieved through a transmission apparatus for a wireless communication system having the features of claim 28, respectively. An important advantage of the invention is that the invention offers a mechanism for the improved use of wireless data links in environments that have to handle fading phenomena by distinguishing between different disturbances of the radio link. Thus, it is possible to achieve an impact of different fade effects in a retransmission scheme since the retransmission scheme depends on the type of disturbance and its reason. Another advantage of the present invention is that it is not limited to a wireless communication system but can be applied to any system where data is transmitted in data packets, examples are GPRS General Packet Service System or the wireless communication system ATM. In addition, the benefits of the invention increase with the increase of the transmission rate since here the course of radio link resources for other users in case of detection of long-term disturbances allows the transfer of an increased amount of data. Globally, in accordance with the invention, retransmission attempts are made only in the case in which there is an opportunity for success. Likewise, in accordance with other aspects of the present invention, this object is achieved through a mobile unit for a wireless communication system in accordance with claim 21. Thus, the mobile unit according to the present invention is adapted to take into account the disturbances that may occur in the radio channel link in the mobile unit to the respective transmission apparatus and this information on the type of disturbance that can be easily derived from the signal received in the mobile unit. Therefore, different disturbances, ie, Rayleigh fading, log-normal fading, loss of propagation fading, etc., can be classified in the mobile unit. According to the present invention, it is proposed to retransmit the information about the type of disturbance to the related transmission apparatus which can therefore avoid any unsuccessful attempt to transmit data packets. Since the acknowledgment message sent by a mobile unit and already contains information classifying the type of disturbance, it is possible to immediately reassign transmission channels within the transmission apparatus without carrying out additional transmission attempts. Likewise, by employing the mobile unit in accordance with the present invention, it is possible to take precaution against different disturbance phenomena with improved monitoring of these disturbance phenomena. Likewise, using the specific location information in the disturbances it is possible to improve the use of scarce radio resources. BRIEF DESCRIPTION OF THE FIGURES. Next, preferred motalities of the present invention will be described with reference to the accompanying drawings in which: Figure 1 shows a schematic diagram of the transmission apparatus according to the present invention; Figure 2 shows a schematic diagram of a mobile unit to be employed within a wireless communication system according to the present invention; Figure 3 shows the angular geometry related to radio channels in a wireless communication system and the analysis of fading phenomena; Figure 4 shows a Rayleigh distribution for a short-term fading; Figure 5 shows a reception field model in an integrated area at a frequency of 100 Mhz and 300 Mhz, respectively; Figure 6 shows an example of the radiation of the amplitude with respect to time according to the Rayleigh fading; Figure 7 shows a log-normal distribution in accordance with the long-term fading phenomena; Figure 8 shows a basic propagation loss in relation to free space in urban areas according to Okumura; Figure 9 shows a height / gain factor of the base station in urban areas according to the range; Figure 10 shows a mobile station height / gain factor in urban areas as a function of frequency and urbanization; Figure 11 shows a basic flow diagram of the retransmission scheme in accordance with the present invention; Figure 12 shows the GPRS reference model of GSM general packet radio services; Figure 13 shows typical routing scenarios within the GSM general packet radio services GPRS illustrated in Figure 12; Figure 14 shows the access procedure as an example of GPRS mobility handling with data packet transfer according to the invention, Figure 15 shows the GPRS routing update process as another example of GPRS mobility handling with data packet transfer according to the present invention; Figure 16 shows an embodiment of the present invention according to which the mobile station derives specific indication data to evaluate the chances of a successful transmission without repeated retransmission attempts; Figure 17 shows a high-level block diagram in a wired ATM network; Figure 18 shows an ATM wireless communication system employing the retransmission scheme in accordance with the present invention; Figure 19 shows a graph of a signal level of its distances from the transmitting antenna; Figure 20 shows a typical environment where a Rayleigh fading occurs; Figure 21 shows a typical environment where a log-normal fading occurs; Figure 22 shows the effect of time dispersion in case of a single impulse transmitted initially, and a typical environment where time dispersion occurs. DESCRIPTION OF PREFERRED MODALITIES Next, various aspects of the retransmission scheme of the present dimension and its application will be described. First, it will describe a transmission apparatus more generally for the application of the transmission scheme of the present invention. Second, another aspect of the present invention relates to a mobile unit that travels in a wireless communication network and is adapted to establish acknowledgment messages indicating to the related transmission apparatus the type of disturbance. Thus, it is possible to avoid retransmission in the transmission apparatus when the acknowledgment already contains information about possible disturbances. Third, several scenarios of the application of the transmission scheme of the present invention, in a wireless communication network GPRS of GSM general packet radio services will be commented taking into account various aspects of communication, i.e., data transfer and management of mobility, respectively. Fourth, the application of the retransmission scheme of the present invention and the transmission apparatus and mobile unit according to the first aspect and the second aspect of the invention to an ATM wireless communication network will be described, with respect to specific examples. Figure 1 shows a schematic diagram of compliance with a transmission apparatus 10 related to the first aspect of the invention. Here, the transmission apparatus 10 comprises a transmitting and receiving unit 12 for transmitting data packets to a moving mobile unit 14 and from said mobile unit which is connected to the transmission apparatus 10 through a radio link.

In addition, the transmission apparatus 10 comprises a transmission monitoring unit 18 connected to an output of the sending and receiving unit 12 to determine whether a transmission between the sending and receiving unit 12 and the mobile unit 14 has been successfully carried out. A transmission channel allocation unit 20 is connected to the transmission monitoring means 18 and serves to change the allocation of radio channels between the transmission apparatus 10 and the mobile units 14. In addition, the transmission channel allocation unit 20 is connected to a channel status unit 22 and table, respectively and also to a table unit of the request 24, respectively. channel 22 is to store the state of the radio link supported by the transmission apparatus 10 by taking, for example, whether it is available or blocked.Also, the request table unit 24 serves to handle a request for mobile units 14 for a channel Next, the function of the transmission apparatus 10 according to the present invention will be described below For this purpose, it can be considered that a radio link channel for the transmission of data packet will be described in FIG. establishes, between, for example, the mobile unit 14-1 and the sending and receiving unit 12 during normal operation, data packets are continuously transmitted between the unit ad 14-1 and the sending and receiving unit 12 while the transmission monitoring unit 18 awaits acknowledgment as shown in Figure 11. Particularly the transmission monitoring unit 18 continuously determines whether a packet transmission of data has been successful or not. If this is not the case, the transmission monitoring unit 18 further determines the possibility of a successful retransmission of the same data packet. An example of such evaluation would be that after several retransmissions it is considered that any additional attempt will not be successful in such a way that additional transmission attempts would cause an additional loss of radio resources. In this case, the transmission monitoring unit 18 will activate the transmission channel allocation unit 20 to switch the communication path to another mobile unit 14-2, ..., 14-n, and radio channel respectively. As shown in Figure 1, there are several ways to implement a reassignment of this type. A direct approach would be to scan the radio link channel 16-1, 16-2, ..., 16-N sequentially. Another option would be to additionally connect the transmit channel allocation unit 20 to a general state table unit 22 to avoid reassignment to a currently blocked radio channel. One reason for this situation would be that a mobile unit 14 is, for example, currently in standby mode and therefore unavailable or that a specific radio channel is reserved for other applications. As shown in Figure 1, each mobile unit 14 is assigned a queue? L,? 2, ...,? N to store requests for an uplink and downlink channel, respectively, on the unit side mobile. Furthermore, in the case in which a mobile unit 14 is not communicating with the sending and receiving unit 12, it can feed the communication requests in the different queues towards the request table unit 24 of the transmission apparatus 10. This allows to reach a higher communication speed between the mobile unit 14 and the transmission apparatus 10 since the transmission channel allocation unit 20 can select the mobile unit 14 to be connected after either directly bypassing the mobile units where the request does not prevail or well by using priorities assigned to different requests in order to avoid any delay for high priority communication requests. As already mentioned above, the first aspect in accordance with the present invention is based on an approach in which a transmission of data packets is repeated until the determination that an additional retransmission will not be successful in the case of the expiration of the pre-established time from the first transmission attempt. A first example would be the case in which a disturbance is not caused by a short-term Rayleigh fading effect but by a log-normal fading effect of longer duration. Here, in the case in which a data packet can not be transmitted for a longer time than a prespecified time, for example, 20 milliseconds, transmission monitoring unit 18 consider that the effect would be longer, such as, for example, 100 milliseconds and therefore consider the disturbance as log-normal fading. If the transmission monitoring unit 18 activates the channel assignment unit 20 after 20 milliseconds have elapsed, the remaining 80 milliseconds can be used for other retransmission attempts thus improving the transmission performance of the transmission device 10 considerably. To perform this first aspect according to the invention, it is required that the acknowledgments received by the mobile unit 14 be sent at time intervals less than the duration of the disturbances, such as, for example, every 10 milliseconds. Another prerequisite in this case is that the data packets have a small size such as ATM cells of 53 bytes in an ATM wireless communication system. As can be seen from the foregoing, the first aspect of the present invention relates to a case in which the transmission apparatus 10 receives only a standard acknowledgment message from the mobile unit 14 without any specific information as for the quality of the radio link between the transmission apparatus 10 and the mobile unit 14. Thus, it is necessary to repeat the transmission at least several times to determine the relative with a retransmission attempt. In accordance with the second aspect of the present invention, it is proposed to avoid such attempts by providing a mobile unit that produces acknowledgment messages containing information regarding the quality of the radio link. Here, it will be noted that obviously such information can usually be derived only on the side of the mobile unit 14, since only here can the real reception conditions for the radio transmission be checked. Figure 2 shows a modality of a mobile unit 14 in accordance with the second aspect of the immension that can provide information as to the strength and characteristic of a received message with an acknowledgment message retransmitted to the transmission apparatus 10, illustrating Figure 1. As shown in Figure 2 the mobile unit 14 comprises a sending and receiving unit 26 for transmitting data packets to the transmission apparatus 10 and from the apparatus 10. Furthermore, the mobile unit 14 comprises a tracking unit. of signals 28 to track the course of the signal received by the sending and receiving unit 26. Further, the mobile unit 14 comprises a transmission analysis unit 30 that receives the signal traced as input and used to determine whether a disturbance has occurred. during signal transmission. Likewise, the transmission analysis unit 30 is adapted to quantify the type of disturbance. In addition, an acknowledgment establishment unit 32 received the signal transmitted from the transmission analysis unit 30 and is adapted to provide an acknowledgment message comprising the type and amount of disturbance that occurred during the transmission of the transmission. a signal. As shown in Figure 2, the acknowledgment setting unit 32 can send the acknowledgment back to the transmission apparatus 10 through the receiving and transmitting unit 26. The main difference between the second aspect of this invention compared to the first aspect described in relation to figure 1 is that due to the insertion of information regarding the type of disturbance in the acknowledgment message retransmitted by the mobile unit 14, a repeated transmission of data packet by the transmission apparatus 10 to detect a disturbance of the radio channel. On the contrary, if an acknowledgment message indicating a disturbance is transmitted by the mobile unit 14 illustrated in FIG. 2 to the transmission apparatus 10 illustrated in FIG., the transmission monitoring unit 18 can immediately activate a reassignment of a transmission channel thus saving unnecessary retransmission attempts and further improving the transmission efficiency within the wireless communication system. Next, details and principles forming the basis of the transmission analysis unit 30 according to the invention will be discussed. For this purpose, a summary of the background theory that forms the basis of the approach of the present invention will also be presented insofar as they relate to the present invention. It will be explained how the transmission analysis 30 and the mobile unit 14 can detect the Rayleigh type fading. According to the present invention, two estimates are provided to determine said Rayleigh fading, that is, the estimate of the distance between two fading minima and in addition, a rate crossover cup of a signal received at a specified level. In general terms, in accordance with the present invention, a first-order estimate of the distance between two fading minima is d =? / 2 (1) where? is the wavelength of the RF signal. This can also be derived from Figure 3 which shows a typical amplitude variation due to Rayleigh fading, where the unit of time is the time to travel through a wavelength. Here, the distance between two minima is approximately d = 16.7 cm for example, for a GSM communication system at f = 900 MHz. The size of the minimum acknowledgment must be estimated at s = 1.67 cm for GSM systems at 900 Mhz. While here a value of conformity with s = d / 10 is specified, in accordance with the present invention any value is suitable if it allows a clear distinction. Considering that a mobile is traveling at a speed v and that the radio signal wavelength is?, The time between two minima is determined as t =? / 2v) = d (2) v Thus, considering the distance of 16.7 cm for a GSM system af = 600 Mhz and considering that a mobile receiver is traveling at a speed of 50 km / h, the time between two flights per fading will be approximately 10.7 ms. Considering that the speed is 5 km / h, the duration of a mobile station in that minimum for fading can be estimated at 16.2 ms. In the case of a wireless communication system operating at 5 GHz, the duration would be 2.16 ms. These figures give an impression of the effects of Rayleigh fading and therefore one can consider the effects of Rayleigh fading as short disturbances, up to 20 ms in duration, as indicated above. Thus, in accordance with this first order estimate for the Rayleigh fading phenomenon, the transmission analysis unit 30 will determine a Rayleigh fading in case of an estimated duration between two fading minima lower than a previously specified threshold value such as, for example, the 20 milliseconds indicated above. In this case, the acknowledgment setting unit 32 will comprise information indicating the distance of a Rayleigh fading phenomenon and also the duration between two Rayleigh fading minima. In this case, the transmission apparatus 10 illustrated in Figure 1 can immediately carry out a reassignment of a radio channel without repeated retransmission attempts. However, as will be illustrated below, the second aspect of the present invention can also be implemented with an improved estimation approach that is based on the characterization of Rayleigh fading with improved accuracy. Particularly, this improved estimation technique is based on an analysis of the received signal in the following manner. In general, a received signal is always (t) is expressed as a product of two parts, the signal subject to long-term fading m (t) and the signal subjected to short-term fading r (t). S (t) = m (t) .r (t) (3) For the analysis of the effects of fading, consider that at each reception point there are N flat waves of equal amplitude of which the Z axis is perpendicular to the plane XY as shown in figure 5. This figure 5 also shows the path angle geometry for the scattered flat wave i-ava. If the transmitted signal is vertically polarized, that is, if the electric field vector is aligned along the Z axis, in the field components in the receiving mobile station are the electric field Ez, the magnetic field Hx, and the magnetic field Hy. These components at the point of reception are expressed in the base panda form of complex equivalent using the Clarke model as ___ E, N H = sm_r, e • > * > 7 _ «_ JP ?? cosffj.e. *, n _T_ where: a = phase angle relative to the plane of the cutter E0 = amplitude of the plane wave N? = Intrinsic wave impedance provided as: where μo = free space magnetic permeability (4pxl0 7) H / m and e0 = electric free space allowance (8,854x10 ~ 12) F / m. Using this model, short and long term fading effects can be analyzed, respectively, by applying the central limit theorem, observing that? and Fx are independent in such a way that Ez, Hx and Hy are complex Gaussian variables. Considering the RF version of equation (4) for the field strength Ez as . < < »> . '*. ») (5) I-í The real part of Ez is provided as Re[. = E0? Cos? Ctcosf -E0? Sin? ./ siníí, (6) 1 = 1 Nf N * LetAc = EB 8s, andA = E. ? smf, then equation (6) can be written as: Re [Ez] = AcC? s? ct -Assin? ct. (7) Since fi is uniformly distributed between 0 and 2p, the mean values of Ac and As are zero and the effective values of Ac and As are _- (.__ 2) = __ (/ -_ 2) = = P. that is, the average received power in the mobile unit. Since A, and As are not correlated, E [AcAs] = 0. Thus, the density of A_ and As follows a normal distribution, and the envelope of A. and As is given by: r = (Ac2 + As2) 1 2 (8) The square root of the sum of the square of the Gaussian functions is the Rayleigh distribution illustrated in figure 5. where: 2P_ = 2s2 is the effective power of the component subject to short-term fading and r2 is the instantaneous power. This Rayleigh probability density function describes the first-order statistics of the signal signal envelope illustrated in Figure 3, particularly at distances sufficiently short for the average level to be considered constant. The first-order statistics are the statistics for which a distance is not a factor and the Rayleigh distribution provides information such as the overall percentage of locations or time during which the envelope is below a specific value. In addition, the Rayleigh distribution allows a quantitative description of the speed with which fading occurs at any depth and the average duration of a fading below a given depth. This information is not only valuable for selecting bit rates of transmission, word length and coding schemes in wireless communication systems, but also allows information on the average duration of fading below a specified level of signal and therefore a analysis of signals received in accordance with the invention. Particularly, an improved approach for estimating disturbances in accordance with the invention is to characterize the Rayleigh phenomenon with the level crossing cups, N (R), of the signal received at the specified signal level R. This signal crossing rate is defined as the average number of times per second that the received signal crosses the level in a positive direction, ie, r > 0, where p (R, r) is the joint probability density function of R and r. Using equation (10), the average level crossing rate at level R illustrated in figure 7 is Since 2s2 = effective value, therefore rms = "V_s is the square root of the effective value The level crossing rate for example, for a vertical on-cone antenna can therefore be provided as follows: N (R) Í2pfjnpe-pl = n0nl (12) where : R R • J2s Therefore, p is the ratio between the specified level and the rms amplitude of the fading envelope, and fm = -,? na ~? / __ TJF n. pe nR is the normalized level crossing independent of the wavelength and speed of the vehicle, v = the speed of the vehicle, and? = carrier wavelength. Preferably, the transmission analysis unit 30 of the invention employs an approximate expression for N (R) as: MR) = -J2p p (13)? Using the above results, the average duration of fades below the specified level R can be found from prob [r = R] E [t? = r (R) = (14 MR) An approximate expression for t (R) to be employed by the transmission analysis unit 30 is provided as:? p t (R) = - - = (16) v J2p Using the formulas and approximations presented above, a calculation of the level crossing rate at a level of -10 dB and the calculation of the average duration of a fading for a digital communication system can be carried out in the following way. 900 MHZ and a vehicle speed of 24 km / h. So, at 900 MHz,? = 3X108 1 .._. 667 = - _n, v = 6.61 m / _, __ = - ^ = 20 Hz 900x106 3"" '""' '"' j" ~~ 3 From figure 7, nR = 0.32 and -10 dB. N (R) = 0.32 x 50 = 16.0 fading / sec. pep2 = nR = 0.32 p = 0.294 t. { R) _ _______ ___ = 0.0061 sec = 6.1 ms 50x0.294 Using the approximate expressions we obtain: level of fading = p = -10dB 20 log p = -10 p = 1 Q-10/20 = 0 # 3 1 62 N (R =? Px ^ x? .3162 = 15.85 fading / sec. 1 0.3162 n _, _. , _. t (R) = r = - = 0.0063 = 6.3 ms 3x6.67 2p Using the techniques and formulas presented above, the transmission analysis unit 30 of the mobile unit 14 according to the second aspect of the present invention allows an estimation of the Rayleigh phenomenon with greater precision. Thus, the implementation of the second aspect of the present invention makes it possible to avoid a wrong reassignment of a radio channel due to a misinterpretation of the conditions in the radio channel. As shown in Figure 9, the second type of fading to be identified by the transmission analysis unit 30 illustrated in Figure 2 is the log-normal fading that results from shading effects, i.e. the use of a mobile unit in an environment with obstacles, for example, an environment of the type illustrated in Figure 21. Here, when considering for example a person disturbing a communication link in an office environment, the duration can be derived from equation (2) with d = 0.2 meters and v = 5 m / ha approximately 144 ms. In addition, a mobile unit 14 traveling on a train traveling through a tunnel would be disturbed for a period of a few seconds. Overall, the events generated by a log-normal fading cause longer disturbances of communication than Rayleigh's fading. Thus, according to the second aspect of the invention, it is proposed to identify log-normal disturbances as long-term disturbances in order to use radio resources for other transmissions where disturbances do not prevail. Thus, the use of wireless links in environments that have to handle fading effects improves considerably. To give an idea of the number of data that can be transmitted additionally in a radio link during a time interval that is equal to the duration of the log-normal disturbances mentioned above, we present some calculations below. A data transmission system at 9.6 kilobits per second transmit 120 bytes in 100 milliseconds; therefore a system that transmits data at 2 megabits per second transmit 25 kilobytes in 100 milliseconds; finally, a system that transmits data at 155 megabits per second transmit it 1.9 megabytes in 100 milliseconds, thus, the consideration of log-normal disturbances in accordance with the invention becomes increasingly important when the frequency of operation is increased to achieve speeds of higher bits within wireless communication systems. The next case to be considered according to the invention is the phenomenon of loss of propagation. This phenomenon occurs when the received signal becomes weaker and weaker due to an increasing distance between the transmission apparatus 10 in the mobile communication system and the moving mobile unit 14. In other words, with the phenomenon of loss of propagation there is no obstacle between the transmitting side and the receiving side, respectively. For this case of free space it is considered that for a given transmission antenna the power density received in the mobile unit 14 is inversely proportional to the square of the distance d between the transmission apparatus 10 and the mobile receiving unit 14, respectively, and also inversely proportional to the square of the transmission frequency f. This leads to a loss of power by space attenuation of Ls ~ d-2. f-2 (17a) or in [dB] Ls (dB) = 33.4 (dB) - 20 log (fMHz) - 20 log (dj_.), (17b) where 33.4 (dB) is a constant of proportionality. It will be noted that this simple formula is valid only for terrestrial mobile wireless communication systems close to the transmission station. A better approximation due to a non-ideal ground plane is that the average signal strength decreases with d ~ 4. However, since the mathematical model of propagation of radio waves in the real world environment is complicated, empirical models have been developed to predict propagation losses. Empirical and semi-empirical models can be created to calculate propagation path losses in urban, semi-urban and rural environments to achieve improved accuracy for perturbation detection in accordance with the invention. According to the invention, if the actual mean value and the strength of the actual signal differ significantly from the predicted average value and the predicted signal strength, this would be an indication of disturbances and consequently of the reassignment of radio resources to other users. of the wireless communication system. Several experimenters have found that natural terrestrial objects affect radio propagation and employ the following characteristics to classify the types of terrestrial objects: building characteristics such as density, height, location and size. It will be noted that no single model can be applied universally in all situations and that the accuracy of a particular model in a given environment depends on the correspondence between the parameters required by the model and the parameters available for the area in question. In general terms, the objective is to predict the average strength of the signal in a small area and the variation and strength of the signal as the mobile unit moves. A prediction model of this type that can be employed within the framework of the present invention is the Okumuara model which is based on the loss of pre-space propagation between the points of interest. Particularly, in the transmission analysis unit 30, the Amu (f, d) value obtained from FIG. 8 showing the pre-stored diagram is added to the loss of free space. mu is the median attenuation relative to free space in an urban area compared to an almost smooth terrain with, for example, an effective base station antenna height is a function of frequency (within the range 100-3,000 MHz) and the distance from the base station (1-100 km). Correction factors such as those illustrated in Figures 9 and 10 are applied to take into account antennas that are not in the reference heights. The basic formulation for the model that is employed in the transmission analysis unit 30 is then. where: L50 is the median loss of propagation, Amu (f, d) = median attenuation in relation to free space in an urban area (see figures 4, 8), Lf = loss of free space, GTu = height gain factor of antenna of base station cmp. figure 8, GRu = mobile antenna height gain factor, cmp. Figure 9. Additional correction factors in graphical form, are used to take into account the orientation of the street and transmission in suburban and rural areas in an irregular terrain. These corrections are added or subtracted as necessary. Irregular terrain is also classified as terrain with rolling hills, isolated mountain, generally sloping terrain, and mixed land-sea trajectory. Additional modes that can be compared to the Okumuara models have been proposed by Sakagmi and Kuboi, Hata, M.F: Ibrahem and J.D. Parsons, and W.C.Y. Lee and these models are described for example in Wireless and Personal Communication System, (Wireless and Personal Communication System), K. Garg and E. Wilkes, Prentice Hall. It will be noted that these models can therefore be used within the scope of the invention and are incorporated herein by reference. Finally, another problem that must be attacked by the transmission apparatus 10 for a wireless communication system according to the invention is the estimation of time dispersion phenomena illustrated in Figure 22. As mentioned above. A radio signal follows a plurality of radio path due to multi-path reflection. Since each path has a different path length, the arrival time for each path is different such that the effect is a diffusion and extension of a signal that is known as a delay or time dispersion extension as shown in figure 22. In a wireless digital communication system, this delay extension causes interference between symbols, thus limiting the maximum symbol speed of a digital multipath channel. Particularly, the main delay extension is defined as where: D (t) is the function of delay probability density and ¡8D. { t) dt = 1 Jo and the typical examples are exponential: 1 - D (t) = - £ -r " uniform: = -f, 0 = t = 2rd D (t) = 0 elsewhere. Here, in the case in which the mobile unit can not handle the scattering phenomenon, for example, through the diverse reception on the receiver side, this fact can again be retransmitted to the transmission apparatus 10 through the message Acknowledgment to achieve a reassignment on the transmission side for a better use of radio resources. A typical example for a case of this type would be the GSM system where the net bit rate at the air interface is 270 kilobits per second leading to a bit time of 3.7 microseconds. Thus, one bit corresponds to 1.1 kilometers in such a way that in the case of a reflection of 1 kilometer behind the mobile unit, the reflected signal will have a longer trajectory of 2 kilometers than the direct path. This means that the reflected signal will mix a signal that combines two time bits after the desired signal with the desired signal. Above, first and second order models to be used for the estimation of different fading phenomena in the mobile unit were described. This makes it possible to derive information regarding the quality of the radio channel already in the mobile unit in such a way that the acknowledgment retransmitted from the mobile unit 14 to the transmission apparatus 10 can provide information as to the type of disturbance in the mobile unit. the radio channel, eventually. Thus, in the event of a disturbance, the transmission apparatus 10 can react immediately to the existing transmission conditions by avoiding unnecessary retransmission attempts. Furthermore, while the present invention was described above in a general manner with regard to the different fading phenomena that may arise in a wireless communication system, specific examples of such wireless communication systems and the application of the invention with relationship to them. The first example concerns the standardization of the general GSM GPRS packet radio service in accordance with - the European Telecommunication Standards Institute (ETSI). GPRS is a new GSM service that offers real radio access in packets for mobile GSM users. According to the GPRS system, radio resources are reserved only when there is algae to send, and the same radio resource is shared by all mobile units in a cedula, which provides an effective use of scarce resources. The GPRS system facilitates several applications such as telemetry, train control systems, interactive data access, charging systems, as well as browsing the Internet through the use of the World Wide Web. Unlike the circuit switched GSM network, the GPRS operation is adapted to offer a connection to a standard data network using protocols such as TCP / IP and X.25. In particular, the GRPS network infrastructure oriented to packet data introduces new functional elements and the concept of mobility management must be adapted. As shown in Figure 12, the GPRS packet-oriented services implemented in accordance with the present invention offer a bearer service from the limit of a data network to a GPRS mobile unit 14. Thus, bearer service users are as for example, IP and X.25 public network layer programmatic packages. Also, specific applications for GPRS will use GPRS services. In the GPRS protocol the layering of the physical radio interface consists of a flexible number of TDMA time slots, ie from 1 to 8 and therefore provides a data path rate of almost 200 Kbit / s. An access control to MAC means using the resources of the physical radio interface and provides a service to the GPRS LLC multiple link control protocol between the mobile unit 14 MS and the service GPRS support mode. The most important features offered by the LLC logical link control protocol are the support in point-to-point addressing and control of the retransmission of data frames is a prerequisite for the present invention., as indicated above. Particularly, LLC data boxes contain fields to control and address, respectively. Usually, only one protocol identifier field and the data field are included in a single LCC box. This data field may consist of PPP point-to-point protocol data frames providing a mechanism independent of the means to exchange different network layer protocol data units in point-to-point link connections and published by the task force of Internet Engineering IETF. Using the structure for data frames presented above, one of the main problems in the mobile communication system GPRS is the routing of data packets to the mobile unit 14 and from the mobile unit 14. This problem can be divided into two problems, routing of data package and mobility management. Accordingly, the retransmission scheme of the present invention presented above applies these routing tasks in the following manner: Particularly, as shown in Figure 12 with the GPRS wireless communication system, the intra-operator structure consists of support nodes , that is, the GPRS gateway support nodes GGSN and the GPRS service support node SGSN. The main function of the GPRS gateway support node GGSN includes the interaction with the external data network. The aforementioned GGSN updates the entertainment direct using the routing information provided by the GPRS SGSN service support nodes in the mobile station path and further routes the encapsulated external data network protocol packet in accordance with the GPRS standard towards the GPRS service support node SGSN currently offering service to the mobile station MS. As shown in Figure 13, the main functions of the GPRS service support node SGSN are the detection of new GPRS mobile units 14 in its service area to handle the registration process of these GPRS mobile units 14 MS in the GPRS registers. , and send / receive data packets to the GPRS 14 units and from the GPRS 14 units. Likewise, the GPRS service support node SGSN keeps a record of a location of the GPRS mobile unit 14 MS within its area of service. The GPRS register acts as a database from which the GPRS service support node SGSN can derive a new GPRS mobile unit 14, can join the GPRS network. As shown in Figure 13 within the GPRS communication system there are three routing schemes and therefore three possible applications for the present invention: originated by the mobile (path 1), terminated in the mobile when the mobile unit GPRS 14 is located in the home network (path 2) and ending in the mobile when the mobile unit GPRS 14 has moved to another GPRS network (path 3). In accordance with the example illustrated in Figure 13, the GPRS network consists of several GPRS gateway support codes GSN and an interoperable structure network. This interoperable structure network connects the support nodes of an operator that employs operator-specific network protocols that may be different for each operator. Using these network creation capabilities, the GPRS gate support node GGSN can be connected to the data network and also to an interoperable structure network connecting the GPRS networks of different operators by using a standard protocol. The main benefit of this architecture is its flexibility, possibility of expansion, as well as its interoperability, that is, each operator can implement an individual structure network using any protocol while communications with other GPRS operators are implemented using only a common protocol. This interoperable protocol is offline due to the nature of the traffic, such as, for example, IPv6 as the main structure protocol proposed by ETSI. In addition, if the present retransmission scheme is applied in an additional way, the effective use of resources and reliability can be considerably improved. As shown in Figure 13, from the perspective of the data network, the GPRS network resembles a subnet of a data network, as, for example, on the Internet the GPRS gateway support node GGSN acts as a gateway to the network. IP, behind which the entire GPRS network is hidden. Thus, the routing mechanism in the data network is exactly the same as in the case of a normal Internet receiver. In accordance with the first example of data routing illustrated in Figure 13 and related to the path 1, the mobile unit GPRS 14 sends a data packet, i.e., a PDU packet data unit of a public switched data network public PSPDN to a data network. The PSPDN PDU data packet is employed employing the LLC protocol in the air interface to the GPRS service support node SGSN that currently serves the GPRS unit 15. In the case in which the GPRS SGSN service support nodes have received the data packet without errors, encapsulates the PSPDN PDU data packet in the GPRS structure network data packet sent to the GPRS gateway support node GGSN which handles traffic from the GPRS mobile unit 14 to data networks. The GPRS gateway support nodes GGSN de-encapsulate into PSPDN PDU data packets and send it to the appropriate data network. Thus, the retransmission scheme of the present invention can also be applied to the GPRS service support node SGSN and the GPRS gate support node GGSN, respectively. From this example, it can be seen that the invention can be applied to successive transmission units during the transfer of the PSPDN PDU data packet between the GPRS mobile unit 14 and the data network, i.e. the GPRS service support node , the GPRS gate support node, and the receiving unit of the data network. According to the invention each of these units can carry out the steps presented above in order to detect an error-free data transmission and switch to another transfer path if a transmission error is detected. As shown in Figure 13, a second example for the application of the invention relates to the path 2 where a guest in a data network is sending a PDP PSPDN data packet to the mobile unit PPRS 14 located in the GPRS network of domicile. Here, in comparison with the first example mentioned above, the PSPDN PDU data packet is routed in the reverse direction using the routing mechanisms in the data network until the PDP PSPDN data packet arrives at the GPRS gateway support node GGSN . In the GPRS gateway support node the PSPDN address of the mobile unit GPRS 14 is extracted and the current location of the GPRS mobile unit 14 is plotted. Then the routing of the PDP data packet PSPDN in the GPRS network is carried out. home. Particularly, the PSPDN PDU data packet is first encapsulated in a structure network and then sent to the GPRS service support node SGSN which is currently serving the mobile unit GPRS 14. Obviously, the transmission scheme of the present invention is applies equally to this case. Here, the GPRS SGSN service support nodes finally remove data related to the network structure and the original PSPDN PDU data packet is sent to the GPRS unit 14 using the MAC / RLC protocol or LLC as presented above. The last example shown in Figure 13 refers to the path 3 and this is identical to the example 2. However, here, the mobile unit 14 has moved to another GPRS network and the home GPRS network must send the PDU data packet PSPDN in the network of structure between operators to the GPRS network visited. A) Yes, in accordance with this example, an additional GPRS gate support node is involved to provide the data packet to the moving GPRS mobile unit 14. Next, the GPRS network typed routes the PDPDN PDU data packet further to the node. appropriate GPRS service support in accordance with what is indicated above in relation to the second example. In addition, the transmission of packets with retransmission in accordance with the present invention is not carried out only in relation to the data transfer according to the examples 1 to 3 illustrated in figure 13, but it is also carried out in relation to the management of GPRS mobility. Here it should be noted that the data packets are transmitted between a GPRS mobile station MS and the GPRS network only in the case in which the GPRS mobile station MS is in the active state. In this active state, the GPRS service gateway support node SGSN knows the location of the cell of the MS GPRS station. Accordingly, if the service support node GPRS SGSN wishes to send a data packet to a mobile station GPRS MS which is in the standby state this mobile station GPRS MS must be called. Since the GPRS support node SGSN knows the routing area where the mobile unit GPRS 14 is located, the packet paging data packet is sent to this routing area. After reception of the packet-paging data packet, the mobile station GPRS MS provides the location of cells to the GPRS service support node SGSN to establish the active state. In accordance with the invention, if the data packet paging data packet transmission is not successful, the retransmission mechanisms presented above can be used to either retransmit the packet paging data packet or to reassign the packet paging channel. transmission to another mobile station GPRS MS. Likewise, a packet data transmission to an active GPRS mobile unit 14 is initiated by a packet paging data packet. Here, the data packet transmission according to the present invention is carried out immediately after the paging of packets through the channel indicated by the packet message. The purpose of the packet paging message is to simplify the process of receiving data packets since the mobile station GPRS MS should only listen to the packet paging message instead of listening to all data packets on all channels. On the contrary, when the mobile unit GPRS 14 has a data packet to be transmitted, access to the uplink channel is required, in such a way that the sender / receiver of the GPRS transmission apparatus receives the data packet. This uplink channel is shared by several mobile stations GPRS MS and its use is assigned by a base station subsystem BSS in the GSM mobile communication system to be related. Here, the mobile station GPRS MS requests the use of the upstream channel through a packet random access message. The base station subsystem BSS allocates an unused channel to the mobile station GPRS MS and sends a packet access grant message in response to the packet random access message. Accordingly, in accordance with the present invention, the retransmission scheme provided to improve the radio resources may also be employed within the GSM communication system, for example, any BSS base station subsystem provided there to improve the use of radio resources. a GPRS network based on its infrastructure. Another case of data transfer between a GPRS mobile unit 14 and several network nodes in accordance with the present invention and related to the handling of GPRS furniture is the execution of the GPRS access procedure when the mobile station GPRS MS is activated as shown in Figure 14. The main purpose of this connection procedure is to send the PSPDN address of the mobile station GPRS MS to the GPRS network, report on the current status of the mobile station GPRS MS, create entries for the assigned PSPDN address in the routing table of the GPRS gateway support node GSN and initiate load and statistics procedures respectively. In particular, during the GPRS connection procedure using the retransmission scheme of the present invention, the context of the logical link between the mobile station GPRS MS and the service support node GPRS SGSN is established using the dedicated dedicated control channel GSM SDCCH as a carrier During the establishment of the context, the mobile station GPRS MS is authenticated and encoding parameters are exchanged between the mobile unit GPRS 14 and the service support node GPRS SGSN this register is sent to the GPRS gateway support node where the location of the mobile station GPRS MS. Here, the GPRS gateway support node GGSN can inform a previous GPRS service support node GSGSN to remove the mobile station GPRS MS from the previous registers. Without the GPRS connection procedure it is successful, the GPRS mobile station enters a standby state. Finally, the mobile station GPRS MS can exit the GPRS service by initiating a GPRS disconnection process. Another process of signaling data packets with retransmission in accordance with the present invention appears in Figure 15 and relates to the GPRS routing update process particularly in the case of an inter-SGSN routing area. As shown in Figure 15, a cell-based routing update procedure is invoked when an active GPRS mobile unit 14 enters a new cell. In this case, the GPRS unit 14 sends a short message data packet containing information as to its movement, i.e., the mobile unit identity GPRS 14 and its new location. The short message data packet is transferred via GPRS transmission channels to its current GPRS SGSN service support node. Thus, it can easily be seen that the present invention of reassigning a transmission channel in the case of specific transmission errors is easily adaptable also to the case of packet-oriented data transfer and in the case in which transmission is not successfully carried out in the case of transmission. GPRS service support node SGSN can switch to provide services to another GPRS mobile station MS that moves in its service area. As shown in FIG. 15, if a GPRS mobile unit 14 is moved from one routing area to another in the service area of a GPRS service support node SGSN, it must again perform a routing update as described in FIG. shows in figure 15 a. If the information is transmitted successfully and if the updated procedure ends, another data packet transfer is initiated for a corresponding response message. Finally, the inter-SGSN routing update illustrated in Figure 15b is the most complicated of the three different routing updates. Here, the mobile station GPRS MS changes from one SGSN area to another and a new connection with a new service support node GPRS SGSN must be established. As shown in Figure 15b, that means creating a new logical link context between the mobile station GPRS MS and the new service support node GPRS SGSN, as well as informing the GPRS gate support node GGSN in the wake of the move. location of the mobile station GPRS MS. Here too, short message data packets can be transmitted using the retransmission scheme of the present invention. - As can be seen from the above, in accordance with the invention a variety of packet transmission processes are carried out within the GPRS network. Here, if detected, the loss of a data packet is addressed through repeated transmission of the data packet. Likewise, if these retransmissions are unsuccessful for longer times, the GPRS communication system of the present invention considers that the disturbance is caused for example by a transmission error of longer duration or a fade effect of longer duration. long . To give an example, if in the GPRS network of the present invention a data packet can not be transmitted for a period greater than 20ms, the GPRS network considers that the duration of the transmission error will last 100 milliseconds or more, since the reason for the disturbance is, for example, a log-normal fading. Within the GPRS network of the present invention the remaining time of 80 ms is not used for further retransmission attempts but is used to send packets of data from any tips to other GPRS mobile units that can be reached. Here, the amount of data packets that can be transmitted obviously depends on the use of the transmission speed. In addition, in accordance with another preferred embodiment of the present invention, location-specific data can be transmitted through the mobile station 14 to the transmission apparatus 10 illustrated in FIG. 1. If the mobile station MS moves in a region in which per se a successful transmission can not be expected, this transmission can be interrupted without the repeated attempts only based on the specific information for location. An example of this type is presented in relation to figure 16. As shown in figure 16, in a region with radio transmission to the GSM network, mobile station 14 receives specific information for location through a channel of CBCH cell broadcast, a BCCH broadcast control channel or in addition a base station identity code BSIC from at least one base station subsystem BSS. Accordingly, accurate information is always available in the mobile station 14 in relation to the current location of the mobile station in the GSM network. In addition, a mobile station MS usually receives location-specific information from the base station subsystem BBS 1 covering the area where it is traveling and also from neighboring subsystems of base stations BSS 2 to BSS 5. The information The indication specification can be used to estimate the geographical position of the mobile system MS and also to transmit the location-specific information to the transmission apparatus 10 illustrated in FIG. 1. In accordance with the example illustrated in FIG. 16, the mobile station MS is moves in a cell 1 and receives direct transmission information from a base station subsystem BSS 1. In addition, the mobile station BSS also receives transmission information from neighboring cells 2 through 5 through base station subsystems Related BSS 2 to BSS 5. An example for calculating location-specific information is shown in Figure 16. c considering that the latitudes of cells 1 to 5 are 1.5, 2.5, 1, 2, 3, respectively and that the corresponding lengths are 2, 2, 1, 1, respectively, the estimated longitude and latitude of the mobile station MS is 2 and 1.4, respectively.

In accordance with this preferred embodiment, the location information is then transmitted to the transmission apparatus 10 wherein the additional transmission quality is determined in advance by complying with the location information. An example would be that the mobile station MS is moving towards a tunnel where the attempts of transmission per se will not be successful and therefore are avoided in general, in order to avoid loss in terms of capacity and time of transformation. Furthermore, as indicated above, the present invention is not limited to a GPRS network, but can also be applied to an ATM wireless communication system. Accordingly, the present invention supports the ongoing evolution of the global wireless structure towards increasing support for broadband multimedia services and the proliferation of radio access based on cellular systems. Likewise, in accordance with the present invention, it is considered an effective use of radio resources for the growing demand for broadband services driven by the use of online services, Internet access, websites worldwide, video on demand , as well as multimedia files where virtual ATM connections are the basis of ongoing developments. Figure 17 shows a high-level block diagram of a wireless ATM network that forms the basis of an ATM wireless communication system according to the present invention. Here, the main components are the ATM ALL adaptation layer, statistical hubs, ATM switches, transmission links, and control computers. Statistical hubs and ATM switches contain buffering buffering to temporarily store incoming data packets that can not be delivered immediately due in the case of a hub to the fact that packets of data generated by active users arrive in parallel , but they are delivered to the output sequentially, or in the case of a switch, because several data packets can arrive in parallel for the same output, but are delivered to this output sequentially. Thus, as a function of time, the number of data packets stored and transmitted by a regularization buffer will rise and fall in accordance with the patterns of generation of data packets from the end users. A typical example for data packets transmitted in this way are 53 bit ATM data packets. In addition, the control computers limit the traffic intensity in the various links in such a way that QoS quality of service guarantees are maintained. For this reason, before receiving a service, a given user must request a connection with the intended recipient and then the admission controller should try to find a route through the network. If such a route can be found, a virtual connection number is assigned for this route and the routing tables in the intervening switches are instructed to route each ATM data packet carrying this virtual connection number within its cell header. The user can then communicate freely in this new established virtual connection. Furthermore, as shown in Figure 17, the AL has the responsibility to convert a user data packet message into a sequence of ATM data packets and to rearm ATM data packets into complete messages. Here, a message can be an individual data package, cmp. Data or image, or a continuous bit stream, for example, voice or video. Unlike the GPRS wireless communication system switched in packets where each connection has an access on request to the resources reserved for this connection, the ATM wireless communication system is a network oriented towards a virtual connection where the resources are not assigned in a exclusive basis, but they are - statistically shared among several connections. Globally, an ATM is based on a virtual VP path to segregate the set of virtual connections into independently manageable groups. Virtual connections that share a common or virtual VP path are known as virtual channels. The VP concept is vital for the creation of a viable admission policy since it divides a large task into separate sets of smaller tasks. As shown in figure 18, the ATM wireless communication system is strongly related to the elements of an ATM network as shown in Figure 17. In particular, this three issues must be managed to allow an ATM wireless communication network. The first issue is the reduction or elimination of the acceptance of a radio link between the mobile unit and the base station, as discussed extensively above in relation to figures 2 to 9. The second issue is the creation within each cell of a high-speed radio channel which can be accessed by the base station and each mobile unit within this cell. Finally, an effective process of handling radio cells allows the use of a large number of smaller cells and therefore of a higher capacity per user. As mentioned above, a main focus of the present invention is the handling of radio link impairments between the mobile unit and the base station. While shading fading can be prevented by varying the transfer of a mobile connection to a cell site that offers less shading, Rayleigh fading and interference from cocanales represents affectations that are too dynamic to be treated by cell transfer . While the present invention has been described using the general description of an ATM wireless communication system, it is easily adapted to the different ATM wireless communication systems currently installed. Examples are the 2.5 GHz band called SUPERNET, an ATM wireless LAN communication system above 10 GHz specified for Europe by the European Telecommunication Standards Institute (ETSI), and also the three ISM bands opened by the Federal Communications Commission (FCC) in the United States of America in accordance with the 950 MHz band, the 2.4 GHz band, and the 5.8 GHz band, respectively, In addition, another example would be the 1.9 band. GHz opened by the FCC for PCS operations.

Claims (29)

1. CLAIMS A transmission apparatus for a wireless communication system, comprising: a) a sending and receiving device (12) for transmitting data packets to at least one moving mobile unit (14) and from at least one mobile unit in travel (14) connected to the transmission apparatus through a radio channel, b) a transmission monitoring device (18) to determine whether a transmission between the sending and receiving device (12) and the mobile unit (14) ) was carried out successfully, characterized in that c) a transmission channel allocation device (20) adapted to reassign a transmission channel to another mobile unit (14) when the transmission monitoring device (18) determines an erroneous transmission and the transmission monitoring device (18) evaluates a repeated transmission of the data packet as unsuccessful. A transmission apparatus according to claim 1, characterized in that the transmission channel allocation device (20) is adapted to reassign the transmission channel based on an acknowledgment received from the mobile unit (14). A transmission apparatus according to claim 1 or 2, characterized in that it further comprises a channel status evaluation device (22) to avoid reassignment to a currently blocked transmission channel. A transmission apparatus according to one of claims 1 to 3, characterized in that it further comprises a transmission request device (24) for identifying the next channel to be used for transmission during operation thereof. with one of claims 1 to 4, characterized in that the transmission monitoring device (18) is adapted to continuously initiate a retransmission through the transmission channel allocation device (20) until a prespecified period has elapsed. of transmission according to claim 5, characterized in that the specified duration is defined as a Rayleigh fading duration: A transmission apparatus according to one of claims 1 to 4, characterized in that the transmission monitoring device (18) is adapted to receive an acknowledgment message from the mobile unit (14) and to initiate a reassignment by the transmission channel allocation device (20) according to the content of the acknowledgment message. 8. A transmission apparatus according to claim 7, characterized in that the transmission channel allocation device (20) reassigns a transmission channel selectively according to the type of disturbance, Rayleigh fading, log-normal fading, loss fading. of propagation, respectively. 9. A transmission device according to one of claims 1 to 8, characterized in that it is a base station (BSC, BTS) or a support node for a general packet service system (GPRS). 10. A transmission device in accordance with. claim 9, characterized in that it is integrated into a mobile switching center (MSC) or a wireless communication system (GSM). A transmission apparatus according to claim 8 or according to claim 9, characterized in that the sending and receiving device (18) transfers logical link control data frames comprising control and direction information, respectively. 12. A transmission apparatus according to claim 8 or according to claim 9, characterized in that the sending and receiving device (18) transmits point-to-point protocol data frames (PPP). 13. A transmission apparatus according to claim 8 or according to claim 9, characterized in that the sending and receiving device (18) transmits packet switched public data units (PSPDN PDU). 14. A transmission apparatus according to one of claims 1 to 7, characterized in that it is a gate support node (GGSN) of a general packet radio service communication (GPRS) system. 15. A transmission apparatus according to one of claims 1 to 7, characterized in that it is a guest in a data network (LAN). 16. A transmission apparatus according to claim 8 or according to claim 9, characterized in that the sending and receiving device (18) transmit packet-paging data packets. A transmission apparatus according to one of claims 1 to 7, characterized in that it is a base station subsystem (BSS) in a GSM digital communication network (GSM) supporting packet-oriented data service (GPRS) and which data packets correspond to packet random access messages and packet access field messages, respectively. 18. A transmission apparatus according to claim 14, characterized in that the sending and receiving device (18) transmits data packet related to GPRS mobility handling as connection processing and routing update, respectively. 19. A transmission apparatus according to one or more of claims 1 to 7, characterized in that it is a buffer in a statistical concentrator, an intermediate memory in an ATM switch, a control computer, and / or a wireless device. adaptation layer in an ATM wireless communication network, respectively. 20. A transmission apparatus according to claim 19, characterized in that the sending and receiving device (18) transmits data packets in the form of an ATM data packet of 53 bytes. 21. A mobile unit for a wireless communication system, comprising: a) a second sending and receiving device (26) for transmitting data packets to a transmission apparatus (10) and from a transmission apparatus (10). ), respectively, b) a signal tracking device (28) for tracking the level of the signal received by the second sending and receiving device (26), characterized by c) a transmission analysis device (30) adapted for identifying a disturbance for the signal received by the second receiving and sending device (26) and for determining a quantization of the disturbance, - d) an acknowledgment setting device (32) adapted to establish an acknowledgment with regard to to the classification and quantification of disturbances produced by the transmission analysis device (30) and to send the acknowledgment through the second device ^ - of reception ion and sent (26) upon the occurrence of a disturbance. 22 A mobile unit in accordance with the claim 21, characterized in that the transmission analysis device (30) is adapted to identify a Rayleigh fading by estimating the time between two local minima of the received signal and comparing this time with a prespecified value. 23. A mobile unit according to claim 21, characterized in that the transmission analysis unit (30) is adapted to estimate the Rayleigh fading phenomena in accordance with an approximate expression for a signal level crossover rate. received in relation to a pre-specified level of analysis. 24. A mobile unit according to claim 21, characterized in that the transmission analysis unit (30) is adapted to estimate a log-normal fading phenomenon by tracking the local average value of the signal received in the second unit of transmission. reception and sending (26) of the mobile unit (14). 25. A mobile unit according to claim 21, characterized in that the transmission analysis unit (30) is adapted to identify a propagation loss phenomenon based on the overall average value of the signal received in the second receiving and sending unit (26) of the mobile unit (14). 26. A mobile unit in accordance with the claim 21, characterized in that the transmission analysis unit (30) is adapted to estimate a propagation loss phenomenon based on the distance between the mobile unit and the respective transmission apparatus / in accordance with Ls (dB) = 33.4 ( dB) - 20 log (fMHz) - 20 log (d? _.). 27. A mobile unit according to claim 21, characterized in that the transmission analysis unit (30) is adapted to estimate the phenomenon of loss of propagation based on the Okumuara model. 28. A method for transmitting data packets in a wireless communication system, comprising the steps of: a) transmitting data packets between a transmission apparatus (10) and a mobile unit (14), respectively, and b) determining whether a transmission of data packets between the transmission apparatus and the mobile unit was carried out successfully, characterized by the step of: c) reassigning a transmission channel to another mobile unit (14) when it is determined that the transmission of the data was not successful and in addition, a retransmission of a data packet is considered unsuccessful. 29. A mobile unit according to claim 28, characterized in that the same data packet is transmitted continuously between the transmission apparatus. (10) and the mobile unit (14) until a predetermined time has elapsed which indicates a long-term disturbance in the radio channel between them. . A method according to claim 28, characterized in that a data packet is retransmitted only when the mobile unit (14) indicates disturbances in the transmission channel through an acknowledgment message. . A method according to claim 30, characterized in that the type of disturbance in the radio channel is determined in the mobile unit according to the local reception conditions.