METHODS FOR TRAFFIC ADMINISTRATION TO MITIGATE INTERFERENCE BETWEEN SIGNALS OF SATELLITE SYSTEMS IN RELATIVE MOTION FIELD OF THE IWVEMTION This invention relates to a method for managing satellite network traffic and in particular to mitigate interference between satellite networks that partially share some channels or common frequencies. It is particularly related to frequency-shared interference between a satellite network, using geosynchronous satellites and a satellite network using non-geosynchronous satellites, or two non-geosynchronous satellite networks, or two non-geosynchronous satellite networks. BACKGROUND OF THE INVENTION Many proprietary communication networks use frequencies from adjacent channels and in some cases share common frequency bands or channels with other communication networks. In wireless communication systems, which use satellite connections, where the satellites of different communication systems experience relative movement with each other, the interference between common or shared channel frequencies may result from relative motion between the satellites of different systems in accordance the geometric distance between two or more directed channels is reduced. This often happens when a system uses REF: 24500
Geosynchronous satellites and another system with shared frequency uses non-geosynchronous satellites. This interference can also occur between two systems each that uses non-geo-synchronous satellites. This interference between the two systems is a pseudo random event that produces undesirable interference between the two systems. This interference degrades customer service. Proposed limits for this degradation are often expressed in terms of interference to noise ratios and percent of time, during which the proportions may be exceeded. A set of these limits is now developed under the auspices of ITU (ie the International Telecommunication Union). It is desirable to avoid this interference to maintain customer satisfaction as well as a need to comply with regulations that limit such interference. COMPENDIUM OF THE INVENTION According to the invention, in an environment of competitive satellite systems (a system using geosynchronous satellites or non-geosynchronous satellites and the other system using non-geosynchronous satellites) having in part shared channel / band frequencies and at least one system that has dedicated bands / channels without interference, the interference between shared bands / channels of the two
systems is mitigated by a method as described in the appended claims. In an illustrative embodiment of the invention, interference probabilities are determined. Based on these probabilities and interference criteria, as established by administrative entities such as ITU, the network usage limits of shared channels are developed. Using these limits, interference is minimized at least by a system that makes initial channel assignments to dedicated channels and allocating shared channels so as not to violate the interference criteria. In a specific application that uses a cascade link band, as known to those known in the art, that has interference in uplink bands only, EIRP (ie Effective Isotropic Radiated Power, maximum transmited power and antenna gain = Irradiated power effective isotropy: antenna gain and maximum transmitted power) is maximized to mitigate the uplink intendency when the uplink / downlink bands are only partially populated. In a cascaded interference analysis (ie there is no signal regeneration between uplink and downlink signals) the noise effects in the uplink and downlink are additive. The total link performance is achieved by keeping the sum of these effects below one
constant determined. By increasing the downlink power available to a user, the effects of noise in the downlink are reduced. Since the sum of the noise effects must be less than a constant, decreasing the effects of downlink interference, allows an increase in the effects of uplink interference for the same total specified performance. This means that the uplink TX power can be reduced (by increasing the effects of uplink noise) by decreasing the amount of interference presented to another system. By always dividing the available downlink power by the number of users (ie maximizing the downlink power per user) the interference during off-peak traffic is greatly reduced. The sum of uplink power ratios "u" and downlink "d" equals regulated power "reg" is related to:
REG.
Additional attenuation, if necessary, is achieved by limiting calls initiated by allowable subscribers. Brief description of the drawing Figure 1 is a schematic of two independent communication systems, each using satellites, in
movement relative to each other and where interference between channels of the two systems may occur; Figure 2 is a schematic block diagram of a stored program processor, which is used to determine interference criteria; Figure 3 is a flow chart and a process for determining limits on channel allocation defined by interference criteria: Figure 4 is a flow diagram for controlling channel allocation according to limits defined by the interference criteria. Detailed DescriptionF * A schematic of two wireless communication systems as illustrated in Figure 1, shows a system that has a geosynchronous connection satellite 101 and the other system that has a non-geosynchronous connection satellite 111. Geosynchronous satellite 101 interconnects two ground stations 102 and 103. The non-geosynchronous satellite 111 connects two ground stations 112 and 113. As indicated by arrow 120, satellite 111 is in relative motion with satellite 101. This relative motion affects the geometric separation of the air interface trajectories of the two systems. While at least one system has dedicated air interference channels, some channels are shared by the two systems. Due to relative movement, the
Shared channels interfere with each other in varying degrees. This interference will be restricted by regulations issued by the ITU agency and other agencies. It is necessary to limit the use of shared channels in a way that conforms to the standards issued. While the illustration shows a particular system, it will be understood that the principles of the invention apply to any system in which satellites of different systems are in relative motion relative to each other. A computing environment as illustrated in Figure 2 provides means to evaluate traffic patterns and convert patterns into a mask to control channel allocation. A stored program storage 201 is connected to the duct 205, to process the allocation of channels and the mask defines the limits developed by this assignment. The conduit 205 connects to the memory 202 by including traffic statistics in the system to which channels are to be assigned. The statistics are processed by the processor 203 to generate the limits defined by the mask and to assign channels according to the mask. The generated assignments are transmitted on the conduit to the controller for assignment of channel 204 that sends out information and in a tangible form or in a way to automatically control channel assignment.
The process of generating boundaries and mask are illustrated in the flow diagram of Figure 3, the terms of the specialty specified below are defined by the ITU and are known by those with skill in the specialty. The process begins at the beginning 301 and in block 303 the geometry of the interference of two systems is accessed. The interference criteria defined by the appropriate administration are accessed in block 305. The frequency assignments of the two systems that identify dedicated and shared channels are provided in block 307. The traffic statistics of the two systems are accessed in the block 309. Initial traffic masks are created based on the traffic patterns of block 311. The frequency planes can be variants with time in which case this process can run in real time to constantly update the traffic mask. The allowable interference to noise ratio, based on the interference criteria, is defined in block 313 and a percentage of the expected interference for these channels is calculated in block 313, to see if the interference criteria are met. In decision block 315, a determination is made as to the need to attenuate and if limits are required to achieve attenuation, they are determined in block 317 by modifying the initial traffic mask of block 311. These limits are
d loqran by reducing the initial traffic mask of the attenuated block 311 to meet the interference criteria, while minimizing the impact on the ability to enter. One method is to reduce all parts of the mask to a minimum percentage, so that the criteria are met. The traffic mask is modified by block 317 to achieve attenuation. A control traffic mask defining channel blocking is outputted according to block 319. The process is terminated at end terminal 321. The control process for channel assignment is illustrated in the flow diagram of Figure 4. After the start terminal 401, the traffic mask is downloaded by the block 403 and the channel assignment is loaded by the block 405. The geometry interference is evaluated to see if it allows interference to occur in the block 407. If it does (yes) the traffic is reassigned or released to meet the interference requirement in block 409. If the geometry does not require interference (no), the flow proceeds to block 411 that responds to requests for channel assignment in the system. Upon receiving a channel assignment request, as determined by decision block 411, a determination is made as to the availability of a dedicated channel in decision block 413. If no channel request is received (no), the flow returns to block 407. If
a dedicated channel is available (if) the assignment is made in accordance with block 423. The flow returns to block 407 after channel assignment. In the absence of a dedicated channel available (no), a less populated shared channel is located in block 415 and the possible use of this channel for assignment is tested, to determine whether it adjusts the mask of the traffic channel allocation (not ), according to block 417 a channel is assigned in block 423. If the mask is exceeded (yes), the request is refused according to block 417 and in block 419 a determination is made as to whether the geometry allows interference. If it does (si) a channel is assigned in block 423 and if not (no), the channel assignment request is rejected in block 421. The flow returns to the power of decision block 407. In instances in the that the channel allocations change in time, the process can be made adaptive by running the process of Figure 3 repetitively, and returning to blocks 409 and 415 via dotted line 424 to block 403 in Figure 4. The process also benefits of the inclusion of satellite ephemeris data and interference geometry. When it is known that interference is impossible, traffic mask restrictions can be removed until the time when the potential for interference again exists.
It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following: