JP3014075B2 - Communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency multiplex communication system. In particular, the present invention realizes a communication network that can efficiently accommodate paths and that has little effect on accommodating new paths and changing paths.

[0002]

2. Description of the Related Art There has been proposed a configuration of a communication network for integrally handling multimedia communication using a plurality of optical wavelengths (for example, S. Kikuchi, et.al, IEEE GLOBECOM 91, Session 3).
4.6, 1991).

FIG. 8 shows a configuration in which multimedia signals of, for example, telephones and TVs are assigned to different wavelengths for communication. This system uses different wavelengths of wavelengths λ _{1 to} λ ₄ , and uses a wavelength division multiplexing technique to divide a subscriber line system into one.
It multiplexes to the subscriber lines and efficiently transmits multimedia signals. Further, in this communication system, since the wavelength division multiplexing is used, signals between respective wavelengths are independent, and for example, there is an advantage that digital signals and analog signals can be transmitted through the same subscriber line.

FIG. 9 shows a frequency allocation of the fixed allocation method of the multimedia signal. In this allocation method, a path of a band f is multiplexed on a center frequency (wavelength) F, and frequency-multiplexed for transmission. This band f is the band of the path. In FIG. 8, the center frequency (wavelength) is fixed irrespective of the band, and each center frequency F _i is a band of f _ch with the adjacent center frequency and bandwidth. The width is taken. This method has an advantage that a path can be easily assigned. However, to accommodate all multimedia signals fixedly, 64 kb / s telephone signals are also 400 Mb / s.
Since the high-definition television signal is also allocated in the same wavelength band, the frequency utilization efficiency is extremely low.

FIG. 10 shows a method of allocating a center frequency in order from the end based on a necessary band. This method is called a variable assignment method, and the wavelength use efficiency on the communication network is ideally enhanced. However, when trying to change the bandwidth of each path, there is a problem that it is necessary to move and change the center wavelength of many paths.

[0006]

As described above, the frequency multiplex path network proposed in the past has a problem that the frequency utilization efficiency is extremely low or that the change of the path band is extremely difficult. For this reason, there has been a demand for a communication system capable of operating a network efficiently and flexibly, even if multimedia traffic can be handled centrally.

An object of the present invention is to provide a communication system which can easily change the band of a path and can efficiently use a frequency.

[0008]

According to the present invention, in a communication system in which signals are mounted on paths of different frequencies and transmission is performed by frequency multiplexing, a frequency for path allocation is divided into a plurality of fixed blocks. , And is not allowed to allocate a path extending between the blocks.

A guard band is provided in each of the divided blocks, a newly accommodated path is allocated to another area except for the guard band, and the guard band is changed only when the band of the already accommodated path is changed. Can be tolerated.

When an unaccommodated path is allocated to a block, a combination that can be accommodated in the block is created in advance from among combinations of paths whose number is equal to or less than a predetermined value unique to each block for the unaccommodated path. , The combination having the widest band can be selected and assigned.

[0011]

According to the present invention, a band to which a path is allocated in the communication network is
It is divided into a plurality of fixed bandwidth blocks. A path is assigned within each of the blocks divided into the blocks. In this case, assignment of a path that extends over blocks is not allowed.

A guard band to which a new path is not allocated is provided in a block, and a new path is not allocated to this guard band. Only the change of the allocation frequency is permitted by the variable assignment method in which the allocation is performed using the guard band.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

Although the following embodiment will be described with reference to a communication system using optical wavelength multiplexing, it is apparent that the present invention can be applied to other frequency multiplexed communication systems.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention and is a frequency arrangement diagram showing wavelength assignments of paths. Here, in the present embodiment, in a communication system in which signals are mounted on paths of different frequencies and transmission is performed by frequency multiplexing, the optical wavelength for path assignment is divided into a plurality of blocks # 1 and # 2 which are fixed bands. It is characterized in that it is divided and the allocation of a path extending between the blocks is not allowed. That is, block # 1 and block # 2
Is not assigned.

Each of the divided blocks accommodates a plurality of wavelength paths, but does not include accommodation between blocks. In the example of FIG. 1, the path # 5 is accommodated in the block # 2 as F6.

As described above, since accommodation of a path spanning between blocks is not allowed, generation and disappearance of a path, and relocation that spans between blocks when changing a band of a path are unnecessary, making it easy to change a path band. Becomes

(Second Embodiment) FIG. 2 is a frequency allocation diagram showing wavelength assignments of paths for explaining a second embodiment of the present invention. In the second embodiment, similarly to the first embodiment, the wavelength of light is divided into wavelength blocks of a fixed band. Here, the feature of the second embodiment is that a band of about 30% is preliminarily set as a margin in the wavelength block and is used as a guard band.

In FIG. 2, each wavelength path is represented by F as a center frequency (wavelength) and f as a required band. The relationship between the required band f and the information amount of the signal that can be modulated on the center frequency F is determined by the performance of the filter and the conditions of the isolation. For example, xbit / s digital information requires a band f of about ± 2 × Hz. Further, a band f of about ± y Hz is required for analog information of y Hz.

FIG. 3 is a flowchart showing the path accommodation operation of the second embodiment. First, the path of the band f _{x (x)}
, The k-th wavelength block is selected from the N wavelength blocks. Then, it is determined whether or not a guard band remains even _if the path (x) of the band fx is accommodated in the k-th wavelength block. If the guard band is left, the path (x) is passed to the k-th wavelength block. x) is accommodated, and if no guard band remains, it is determined whether or not the next wavelength block can be accommodated, and a wavelength path block that can accommodate the path of the band f (x) without using the guard band is searched. And accommodate.

FIG. 4 is a flowchart showing the operation of changing the bandwidth of a path in the second embodiment. This is an example of when you want to increase the bandwidth of the path x to be changed to f _x 'from f _x. First, it is determined whether or not the change can be made in the currently accommodated wavelength block. If the change is possible in the currently accommodated wavelength block, the band is changed to f _x ′. In this case, the use of the guard band is permitted in the currently accommodated wavelength block, and the change of the band is permitted if the band can be accommodated even by using the guard band. If the wavelength cannot be changed within the wavelength block, the accommodation is switched to another wavelength block. In this case, the use of the guard band is not permitted.

FIG. 5 shows another example of path assignment in a wavelength block. This is for avoiding the shift of the center frequency of the path in the same wavelength block when the path band f is slightly changed, so that a margin is provided between the paths.
When the band is slightly changed, the band is changed without moving the center frequency F. However, in this embodiment, the assignment of the path itself is basically a method of performing variable assignment.

(Third Embodiment) Next, a third embodiment will be described with reference to FIG. 6 which shows a flowchart of an assignment operation when a plurality of new paths are accommodated in a wavelength block.

In the third embodiment, when a plurality of paths are accommodated in a wavelength block, one wavelength block is selected and the path assignment is repeated so that the block becomes full. The path assignment defines a certain threshold n, making all combinations of 1 to n paths,
Among them, a combination with the widest occupied band is to be selected.

In FIG. 6, for example, n = 2 as the threshold value n
It is assumed that the wavelength path block has five paths to be accommodated. A combination of n or less paths constituted by unaccommodated paths is created. Assuming that these five paths require f ₁ , f ₂ , f ₃ , f ₄ , and f ₅ as bands, respectively, the combination is f ₁ , f ₁ + f ₂ , f ₁ +
_{f 3, f 1 + f 4} , f 1 + f 5, f 2, f 2 + f 3, f
_{2 + f 4, f 2 +} f 5, f 3, f 3 + f 4, f 3 +
_{f 5, f 4, f 4} + f 5, the f ₅ ways. Among these combinations, a combination of paths that can be accommodated in the wavelength path block and has the largest occupied bandwidth is selected. If the band is the same, the one with the smaller number of constituent paths is preferentially selected. As described above, in this embodiment, by appropriately selecting n, it is possible to efficiently use a band to accommodate a path.

FIG. 7 shows a simulation result of the path arrangement according to the present invention. Here, the bandwidth of the wavelength block is set to 20.
The probability that the rearrangement of paths is required to be performed between the wavelength blocks when the bandwidth of the guard band is set to GHz and the bandwidth of the guard band is set to the horizontal axis is shown on the vertical axis. In addition, it is assumed that the paths are distributed from 0.1 GHz to 8.4 GHz, respectively. At this time, for example, the guard band is set to 4.5.
Assuming GHz, the probability of having to be rearranged between the wavelength blocks is approximately 0.1, and approximately 90% of the bandwidth change of the path is possible by the bandwidth change within the wavelength block. However, for example, if the guard band is 1 GHz, the changeable path is reduced to almost 60%.
Therefore, by providing sufficient guard bands,
Flexible assignment of paths within a wavelength block is possible.

[0027]

As described above, according to the present invention, the path can be variably accommodated independently in one frequency block. Therefore, the change of the band of the path in that block is performed by the variable assignment for moving the center frequency. Is possible, so that the reallocation of the band is easy. Further, since the path can be packed in the block, the frequency can be used efficiently. As a result, the present invention can provide a communication method that can efficiently accommodate paths and can flexibly respond to changes in path bandwidth.

[Brief description of the drawings]

FIG. 1 is a diagram showing a frequency arrangement according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a frequency allocation according to a second embodiment of the present invention.

FIG. 3 is a flowchart illustrating path accommodation according to a second embodiment.

FIG. 4 is a flowchart illustrating band change according to the second embodiment.

FIG. 5 is a diagram showing another frequency arrangement of the second embodiment.

FIG. 6 is a flowchart illustrating path accommodation according to the third embodiment.

FIG. 7 is a diagram showing a pass band change probability by a guard band according to the present invention.

FIG. 8 is a diagram showing a configuration of a multimedia communication system.

FIG. 9 is a frequency allocation diagram showing a conventional fixed assignment method.

FIG. 10 is a frequency allocation diagram showing a conventional variable assignment method.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04J 1/00

Claims (3)

(57) [Claims] 1. Each signal on a path of a different frequency
On-board communication system with frequency multiplex transmission
Divides the frequency for path assignment into fixed blocks
AndGuard bands are set in each of the divided blocks.
Ke The newly accommodated path is in other areas except this guard band
To change the bandwidth of the already accommodated path.
Only allow guard bands to be assigned, Do not allow path assignments between blocks
 A communication method characterized by that: 2. In a communication system in which signals are mounted on paths of different frequencies and transmission is performed by frequency multiplexing, a frequency for path allocation is divided into a plurality of fixed blocks, and an unaccommodated path is divided into blocks. When allocating, in advance, a combination that can be accommodated in the block is created among combinations of paths equal to or less than a predetermined value specific to each block for an unaccommodated path, and a combination having the widest band is selected and assigned, A communication method, wherein assignment of a path extending between the blocks is not allowed. 3. A guard band is provided in each of the divided blocks, a newly accommodated path is allocated to another area excluding the guard band, and the guard band is changed only when the band of the already accommodated path is changed. Claim 2 permitting assignment to
The communication method described.