JP6227990B2

JP6227990B2 - Wireless signal transmission system, master device, remote device, and transmission method

Info

Publication number: JP6227990B2
Application number: JP2013254944A
Authority: JP
Inventors: 桑野　茂; 茂桑野; 淳一可児; 陽一深田; 寺田　純; 純寺田
Original assignee: Nippon Telegraph and Telephone Corp
Current assignee: Nippon Telegraph and Telephone Corp
Priority date: 2013-12-10
Filing date: 2013-12-10
Publication date: 2017-11-08
Anticipated expiration: 2033-12-10
Also published as: JP2015115693A

Description

本発明は、ＲＯＦ（ＲａｄｉｏｏｖｅｒＦｉｂｅｒ）を用いた無線信号伝送システムにおいて、高品質かつ経済的に広帯域の無線信号を伝送する技術に関する。 The present invention relates to a technique for transmitting a high-quality, economically wide-band wireless signal in a wireless signal transmission system using ROF (Radio over Fiber).

ＬＴＥ（ＬｏｎｇＴｅｒｍＥｖｏｌｕｔｉｏｎ）を始めとするセルラ構成を用いたブロードバンドワイヤレスシステムの進展が著しい。このようなセルラのブロードバンドワイヤレスシステムでは、様々な環境にいる多くのユーザに対してより広帯域なサービスを効率的に提供するため、セルサイズを縮小したスモールセル構成をとる傾向があり、カバレッジを維持するためセル数が増加する。 The progress of broadband wireless systems using a cellular configuration including LTE (Long Term Evolution) is remarkable. In such cellular broadband wireless systems, there is a tendency to adopt a small cell configuration with a reduced cell size in order to efficiently provide a wider band service to many users in various environments, thus maintaining coverage. This increases the number of cells.

多くのセルを設置するためには、基地局のサイズを縮小することが必要であり、無線基地局を無線変復調部と無線送受信部に分割した分散アンテナ構成がとられる。この場合、アンテナの近傍に設置される無線送受信部を小型化することが可能であり、効率的な設置が可能となる。 In order to install many cells, it is necessary to reduce the size of the base station, and a distributed antenna configuration in which the radio base station is divided into a radio modulation / demodulation unit and a radio transmission / reception unit is adopted. In this case, the wireless transmission / reception unit installed in the vicinity of the antenna can be reduced in size, and efficient installation becomes possible.

このような分散アンテナ構成において、無線変復調部１１と無線送受信部２１の間で高精度に無線信号を伝送する必要があり、かつ長距離を伝送する必要もあるため、伝送路として光ファイバ伝送路１４を用いたＲＯＦシステムが用いられる。ＲＯＦシステムの実現手段としては、無線信号をそのままアナログ伝送するアナログＲＯＦ（図１）およびデジタル化した無線信号をデータとして伝送するデジタルＲＯＦ（図２）がある。 In such a distributed antenna configuration, it is necessary to transmit a radio signal with high accuracy between the radio modulation / demodulation unit 11 and the radio transmission / reception unit 21 and to transmit a long distance. ROF system using 14 is used. As means for realizing the ROF system, there are an analog ROF (FIG. 1) for transmitting a wireless signal as it is and a digital ROF (FIG. 2) for transmitting a digitized wireless signal as data.

アナログＲＯＦでは、光インタフェース１３において無線変調信号でアナログ光変復調し、無線信号を光ファイバ伝送路１４上で伝送する。また、デジタルＲＯＦでは無線変調信号をデジタル化し、デジタルデータを光インタフェース１３で光信号に変換し、光ファイバ伝送路１４を伝送する。関連技術ではＲＯＦ区間を低コストかつ高品質で伝送できることからデジタルＲＯＦを用いたＣＰＲＩ（ＣｏｍｍｏｎＰｕｂｌｉｃＲａｄｉｏＩｎｔｅｒｆａｃｅ）（非特許文献１）を用いたシステム（図３）が広く実用に供されている。 In the analog ROF, analog optical modulation / demodulation is performed with a radio modulation signal in the optical interface 13, and the radio signal is transmitted on the optical fiber transmission line 14. In the digital ROF, the radio modulation signal is digitized, the digital data is converted into an optical signal by the optical interface 13, and transmitted through the optical fiber transmission line 14. In the related art, since a ROF section can be transmitted at a low cost and with high quality, a system using a digital public interface (CPRI) (Non-Patent Document 1) (FIG. 3) is widely used.

例えば、ＬＴＥでの２０ＭＨｚ帯域の２アンテナ分の無線信号を伝送するのに、２．５Ｇｂ／ｓ帯域のＣＰＲＩ回線が用いられている。なお、ＣＰＲＩは独自の伝送フォーマットを用いているため、ダークファイバ等の専用の伝送媒体を用いる必要がある。 For example, a 2.5 Gb / s band CPRI line is used to transmit radio signals for two antennas in the 20 MHz band in LTE. Since CPRI uses a unique transmission format, it is necessary to use a dedicated transmission medium such as dark fiber.

ＣＰＲＩＳｐｅｃｉｆｉｃａｔｉｏｎＶ５．０，Ｓｅｐｔｅｍｂｅｒ２０１１（“１．Ｉｎｔｒｏｄｕｃｔｉｏｎ”， “２．１．Ｄｅｆｉｎｉｔｉｏｎｓ／Ｎｏｍｅｎｃｌａｔｕｒｅ”）．CPRI Specification V 5.0, September 2011 (“1. Introduction”, “2.1. Definitions / Nomenclature”).

ＬＴＥの発展形であるＬＴＥ−Ａ（ＬＴＥａｄｖａｎｃｅｄ）では、より広帯域（〜１００ＭＨｚ）の信号の伝送が必要となるとともに、ＭＩＭＯ（ＭｕｌｔｉＩｎｐｕｔＭｕｌｔｉＯｕｔｐｕｔ）による空間での多重度が増加するため、より多くのアンテナが必要となる。 LTE-A (LTE advanced), which is an extension of LTE, requires transmission of a wider band (up to 100 MHz) and increases the multiplicity in the space by MIMO (Multi Input Multi Output). Many antennas are required.

このため、ＣＰＲＩに要求される帯域も増大し、セルあたりで１００Ｇｂ／ｓ以上の帯域が必要となり、インタフェースコストやファイバコストが増大してしまう。４０Ｇｂ／ｓや１００Ｇｂ／ｓの高速インタフェースを用いる場合、受信感度が低下し誤り訂正符号を用いないと伝送が困難である。 For this reason, the bandwidth required for the CPRI also increases, and a bandwidth of 100 Gb / s or more is required per cell, which increases the interface cost and the fiber cost. When a high-speed interface of 40 Gb / s or 100 Gb / s is used, reception sensitivity is lowered, and transmission is difficult unless an error correction code is used.

しかし、誤り訂正符号の信号処理による遅延時間はＣＰＲＩの装置に許容される遅延時間（３．５ｕｓ）より大きいため、インタフェース速度を高速化することは難しい。また、波長多重（ＷＤＭ：ＷａｖｅｌｅｎｇｔｈＤｉｖｉｓｉｏｎＭｕｌｔｉｐｌｅｘｉｎｇ）によりファイバ数を削減することも可能であるが、将来の無線システムではさらに帯域が増大することが想定されるため、伝送容量の限界が生じてしまう。 However, since the delay time due to the signal processing of the error correction code is longer than the delay time (3.5 us) allowed for the CPRI device, it is difficult to increase the interface speed. In addition, the number of fibers can be reduced by wavelength division multiplexing (WDM). However, in a future wireless system, it is assumed that the band will be further increased, and thus the transmission capacity is limited.

一方、アナログＲＯＦを用いる場合、所要帯域幅は無線信号の帯域幅であるため、伝送容量的には問題ないが、光伝送による雑音や非線形歪み等により信号品質の劣化が生じ、多チャネルや多値数の多い変調方式の適用は困難となる。また、リモート側の装置の監視制御が課題となる。 On the other hand, when an analog ROF is used, the required bandwidth is that of a radio signal, so there is no problem in terms of transmission capacity, but signal quality deteriorates due to noise, nonlinear distortion, etc. due to optical transmission, resulting in multiple channels and multiple channels. It is difficult to apply a modulation method having a large number of values. Also, monitoring control of the remote device becomes an issue.

前記課題を解決するために、本発明は、無線信号伝送システムにおいて、光伝送で生じる下り光信号の非線形歪ならびに波形劣化をマスタ装置が備える予補償回路及びリモート装置が備える補償回路におけるデジタル信号処理で補償することを目的とする。 In order to solve the above-described problems, the present invention provides a digital signal processing in a precompensation circuit provided in a master device and a compensation circuit provided in a remote device for nonlinear distortion and waveform degradation of a downstream optical signal caused by optical transmission in a wireless signal transmission system. The purpose is to compensate.

上記目的を達成するため、本発明の無線信号伝送システムでは、マスタ装置が、予め算出した歪み補償量を電気信号に加算して歪み補償を行い、歪み補償した伝送信号をリモート装置で歪み量を検出し、検出した歪み量を補償する。 In order to achieve the above object, in the wireless signal transmission system of the present invention, the master device performs distortion compensation by adding the distortion compensation amount calculated in advance to the electrical signal, and the distortion compensation transmission signal is corrected by the remote device. Detect and compensate for the detected distortion.

具体的には、本発明に係る無線信号伝送システムは
予め算出した歪み補償量を電気信号に加算し、加算した前記電気信号を下り光信号に変換し、光伝送路を介して接続されたリモート装置に前記下り光信号を送信するマスタ装置と、
前記マスタ装置が送信した前記下り光信号を受信するとともに、受信した前記下り光信号を電気信号に変換し、前記電気信号の歪み量を検出し、検出した前記歪み量を補償し、補償した電気信号を無線信号に変換して外部に出力するリモート装置と、を備える。 Specifically, the radio signal transmission system according to the present invention adds a distortion compensation amount calculated in advance to an electrical signal, converts the added electrical signal into a downstream optical signal, and connects the remote signal connected via the optical transmission path. A master device for transmitting the downstream optical signal to a device;
The downstream optical signal transmitted by the master device is received, the received downstream optical signal is converted into an electrical signal, the amount of distortion of the electrical signal is detected, the detected amount of distortion is compensated, and the compensated electrical A remote device that converts the signal into a radio signal and outputs the signal to the outside.

本発明に係る無線信号伝送システムでは、
前記マスタ装置は、
予め生成された監視制御信号をマスタ装置側周波数変換回路に出力するマスタ装置側監視制御回路と、
前記マスタ装置が備えるデジタル無線変調回路が出力したデジタル電気信号に、前記監視制御信号を多重するマスタ装置側周波数変換回路と、をさらに備え、
前記リモート装置は、
前記マスタ装置側周波数変換回路で多重された前記監視制御信号を抽出し、抽出した前記監視制御信号をリモート装置側監視制御回路に出力するリモート装置側周波数変換回路と、
前記監視制御信号に応じて前記リモート装置の設定変更及び制御を行う前記リモート装置側監視制御回路と、をさらに備えてもよい。 In the wireless signal transmission system according to the present invention,
The master device is
A master device-side monitoring control circuit that outputs a pre-generated monitoring control signal to the master device-side frequency conversion circuit;
A master device-side frequency conversion circuit that multiplexes the monitoring control signal with the digital electrical signal output by the digital radio modulation circuit included in the master device;
The remote device is
A remote device side frequency conversion circuit that extracts the monitoring control signal multiplexed by the master device side frequency conversion circuit, and outputs the extracted monitoring control signal to a remote device side monitoring control circuit;
The remote device-side monitoring control circuit that performs setting change and control of the remote device according to the monitoring control signal may be further included.

本発明に係る無線信号伝送システムでは、
前記マスタ装置側監視制御回路は、
前記デジタル無線変調回路が出力したデジタル電気信号に基準クロックを多重し、
前記リモート装置側周波数変換回路は、
前記マスタ装置側監視制御回路で多重された前記基準クロックを抽出し、前記基準クロックに応じて前記リモート装置内の基準クロックと周波数同期してもよい。 In the wireless signal transmission system according to the present invention,
The master device side monitoring control circuit,
A reference clock is multiplexed onto the digital electrical signal output by the digital radio modulation circuit,
The remote device side frequency conversion circuit is:
The reference clock multiplexed by the master device side monitoring control circuit may be extracted and frequency-synchronized with the reference clock in the remote device according to the reference clock.

具体的には、本発明に係るマスタ装置は
デジタル電気信号を出力するデジタル無線変調回路と、
前記デジタル電気信号を予め定められた中間周波数帯域に変換するとともにサンプリングレート変換するマスタ装置側周波数変換回路と、
予め算出した歪み補償量を前記マスタ装置側周波数変換回路で変換されたデジタル電気信号に加算する予補償回路と、
前記歪み補償量が加算されたデジタル電気信号をアナログ電気信号に変換するマスタ装置側デジタルアナログ変換回路と、
前記アナログ電気信号を光変調し、光変調した下り光信号を送信する光送信回路と、を備える。 Specifically, the master device according to the present invention includes a digital wireless modulation circuit that outputs a digital electrical signal,
A master device-side frequency conversion circuit that converts the digital electrical signal into a predetermined intermediate frequency band and converts the sampling rate;
A precompensation circuit for adding a distortion compensation amount calculated in advance to the digital electrical signal converted by the master device side frequency conversion circuit;
A digital-analog conversion circuit on the master device side that converts the digital electrical signal to which the distortion compensation amount is added into an analog electrical signal; and
An optical transmission circuit that optically modulates the analog electrical signal and transmits the optically modulated downstream optical signal.

本発明に係るマスタ装置では、
予め生成された監視制御信号を前記マスタ装置側周波数変換回路に出力するマスタ装置側監視制御回路をさらに備え、
前記マスタ装置側周波数変換回路が、前記デジタル無線変調回路で出力したデジタル電気信号に前記監視制御信号を多重してもよい。 In the master device according to the present invention,
A master device-side monitoring control circuit that outputs a pre-generated monitoring control signal to the master device-side frequency conversion circuit;
The master device-side frequency conversion circuit may multiplex the monitoring control signal with the digital electric signal output from the digital radio modulation circuit.

具体的には、本発明に係るリモート装置は
マスタ装置が送信した下り光信号を受信し、アナログ電気信号に変換する光受信回路と、
前記光受信回路で変換したアナログ電気信号をデジタル電気信号に変換するアナログデジタル変換回路と、
前記マスタ装置が備える予補償回路で加算された前記デジタル電気信号の歪み補償量を検出するとともに前記歪み補償量以外の歪み量を検出し、検出した前記歪み補償量及び前記歪み量を補償する補償回路と、
前記歪み補償量及び前記歪み量を補償したデジタル電気信号を出力するリモート装置側周波数変換回路と、
前記リモート装置側周波数変換回路が出力した前記デジタル電気信号をアナログ電気信号に変換するリモート装置側デジタルアナログ変換回路と、
前記リモート装置側デジタルアナログ変換回路で変換した前記アナログ電気信号を無線信号に変換し外部に出力する無線送信回路と、を備える。 Specifically, the remote device according to the present invention receives a downstream optical signal transmitted by the master device and converts it into an analog electrical signal;
An analog-digital conversion circuit that converts the analog electrical signal converted by the optical receiver circuit into a digital electrical signal;
Compensation for detecting the distortion compensation amount of the digital electric signal added by the pre-compensation circuit included in the master device, detecting a distortion amount other than the distortion compensation amount, and compensating the detected distortion compensation amount and the distortion amount. Circuit,
A remote device side frequency conversion circuit for outputting the distortion compensation amount and the digital electric signal compensated for the distortion amount;
A remote device side digital-analog conversion circuit for converting the digital electric signal output by the remote device side frequency conversion circuit into an analog electric signal;
A wireless transmission circuit that converts the analog electrical signal converted by the digital analog conversion circuit on the remote device side into a wireless signal and outputs the signal to the outside.

本発明に係るリモート装置では、
リモート装置側監視制御回路をさらに備え、
前記リモート装置側周波数変換回路が、前記マスタ装置が備えるマスタ装置側周波数変換回路で多重された監視制御信号を抽出し、抽出した前記監視制御信号を前記リモート装置側監視制御回路に出力し、
前記リモート装置側監視制御回路が、前記監視制御信号に応じて前記リモート装置の設定変更及び制御してもよい。 In the remote device according to the present invention,
A remote device side monitoring control circuit is further provided,
The remote device side frequency conversion circuit extracts the monitoring control signal multiplexed by the master device side frequency conversion circuit included in the master device, and outputs the extracted monitoring control signal to the remote device side monitoring control circuit,
The remote device monitoring control circuit may change and control the setting of the remote device in accordance with the monitoring control signal.

具体的には、本発明に係る無線信号伝送システムの伝送方法は、
予め算出した歪み補償量を電気信号に加算し、加算した前記電気信号を下り光信号に変換して、マスタ装置からリモート装置に光伝送路を介して前記下り光信号を送信する光信号送信手順と、
前記マスタ装置が送信した前記下り光信号を前記リモート装置で受信するとともに、受信した前記下り光信号を電気信号に変換し、前記電気信号の歪み量を検出し、検出した歪み量に基づいて算出した歪み補償量を前記電気信号に加算して歪み量を補償し、補償した電気信号を無線信号に変換して外部に出力する無線信号出力手順と、を順に有する。 Specifically, the transmission method of the wireless signal transmission system according to the present invention is:
An optical signal transmission procedure for adding a distortion compensation amount calculated in advance to an electrical signal, converting the added electrical signal into a downstream optical signal, and transmitting the downstream optical signal from the master device to a remote device via an optical transmission path When,
The downstream optical signal transmitted by the master device is received by the remote device, the received downstream optical signal is converted into an electrical signal, the amount of distortion of the electrical signal is detected, and the calculation is based on the detected amount of distortion. A wireless signal output procedure for adding the corrected distortion compensation amount to the electrical signal to compensate for the distortion amount, converting the compensated electrical signal into a wireless signal, and outputting the signal to the outside.

なお、上記各発明は、可能な限り組み合わせることができる。 The above inventions can be combined as much as possible.

本発明によれば、ＲＯＦを用いた無線信号伝送システムにおいて、高品質かつ経済的に広帯域の無線信号を伝送することが可能となる。 According to the present invention, it is possible to transmit a broadband wireless signal with high quality and economically in a wireless signal transmission system using ROF.

関連技術におけるアナログＲＯＦの一例を示す。An example of analog ROF in related technology is shown. 関連技術におけるデジタルＲＯＦの一例を示す。An example of the digital ROF in related technology is shown. 関連技術におけるＣＰＲＩシステムの一例を示す。An example of the CPRI system in related technology is shown. 本実施形態に係る無線信号伝送システムの構成の一例を示す。1 shows an exemplary configuration of a wireless signal transmission system according to the present embodiment. 本実施形態に係る予補償回路の構成の一例を示す。2 shows an example of a configuration of a pre-compensation circuit according to the present embodiment. 本実施形態に係る補償回路の構成の一例を示す。2 shows an exemplary configuration of a compensation circuit according to the present embodiment. 本実施形態に係るリモート装置の構成の一例を示す。2 shows an example of the configuration of a remote device according to the present embodiment. 本実施形態に係るマスタ装置の周波数変換の一例を示す。An example of the frequency conversion of the master apparatus which concerns on this embodiment is shown. 本実施形態に係るリモート装置での周波数変換の一例を示す。An example of frequency conversion in the remote device according to the present embodiment is shown. 本実施形態に係るリモート装置での周波数変換の一例を示す。An example of frequency conversion in the remote device according to the present embodiment is shown. 本実施形態に係るリモート装置での基準クロック抽出の一例を示す。An example of reference clock extraction in the remote device according to the present embodiment is shown. 本実施形態に係るリモート装置での周波数同期の一例を示す。An example of the frequency synchronization in the remote apparatus which concerns on this embodiment is shown.

以下、本発明の実施形態について、図面を参照しながら詳細に説明する。なお、本発明は、以下に示す実施形態に限定されるものではない。これらの実施の例は例示に過ぎず、本発明は当業者の知識に基づいて種々の変更、改良を施した形態で実施することができる。なお、本明細書及び図面において符号が同じ構成要素は、相互に同一のものを示すものとする。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below. These embodiments are merely examples, and the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. In the present specification and drawings, the same reference numerals denote the same components.

（第１の実施形態）
本実施形態に係る、無線信号伝送システムは、光伝送路を介して接続されたマスタ装置及びリモート装置を備える。マスタ装置は、リモート装置に対し下り光信号を送信し、リモート装置が受信する。また、無線信号伝送システムにおける下り光信号の伝送方法は、マスタ装置が行う光信号送信手順と、リモート装置が行う無線信号出力手順と、を順に有する。光信号送信手順では、マスタ装置が歪み補償量を電気信号に加算し電気信号を下り光信号に変換してリモート装置に送信する。リモート装置における無線信号出力手順では、受信した下り光信号を電気信号に変換し、電気信号の歪みを検出し、検出した歪みに基づいて算出した歪み補償量を電気信号に加算して波形歪を補償した電気信号を無線信号に変換して外部に出力する。 (First embodiment)
The wireless signal transmission system according to the present embodiment includes a master device and a remote device connected via an optical transmission path. The master device transmits a downstream optical signal to the remote device, and the remote device receives it. Further, the downstream optical signal transmission method in the wireless signal transmission system includes an optical signal transmission procedure performed by the master device and a wireless signal output procedure performed by the remote device in this order. In the optical signal transmission procedure, the master device adds the distortion compensation amount to the electrical signal, converts the electrical signal into a downstream optical signal, and transmits it to the remote device. In the radio signal output procedure in the remote device, the received downstream optical signal is converted into an electric signal, distortion of the electric signal is detected, and a distortion compensation amount calculated based on the detected distortion is added to the electric signal to reduce waveform distortion. The compensated electrical signal is converted into a radio signal and output to the outside.

図４に本発明の第１の実施形態を示す。本実施形態は、デジタル無線変調回路５２、予補償回路５４、マスタ装置側周波数変換回路として機能する周波数変換回路５３、マスタ装置側デジタルアナログ変換回路として機能するデジタルアナログ変換回路５５、光送信回路５６および監視制御回路５７とから構成されるマスタ装置５１と、光受信回路６２、アナログデジタル変換回路６３、補償回路６４、リモート装置側周波数変換回路として機能する周波数変換回路６５、リモート装置側デジタルアナログ変換回路として機能するデジタルアナログ変換回路６６、無線送信回路６７および監視制御回路６８とから構成されるリモート装置６１と、マスタ装置５１とリモート装置６１を接続する光伝送路５８とから構成される。 FIG. 4 shows a first embodiment of the present invention. In the present embodiment, a digital radio modulation circuit 52, a precompensation circuit 54, a frequency conversion circuit 53 that functions as a master device side frequency conversion circuit, a digital analog conversion circuit 55 that functions as a master device side digital analog conversion circuit, and an optical transmission circuit 56 And a master control unit 51 comprising a monitoring control circuit 57, an optical receiving circuit 62, an analog-digital conversion circuit 63, a compensation circuit 64, a frequency conversion circuit 65 functioning as a remote device side frequency conversion circuit, and a remote device side digital-analog conversion The remote device 61 includes a digital-analog conversion circuit 66 that functions as a circuit, a wireless transmission circuit 67, and a monitoring control circuit 68, and an optical transmission path 58 that connects the master device 51 and the remote device 61.

マスタ装置５１のデジタル無線変調回路５２で出力したデジタル電気信号であるデジタル無線変調信号は、マスタ装置側周波数変換回路として機能する周波数変換回路５３で適当な中間周波数帯にデジタル周波数変換ならびにサンプリングレート変換された後、予補償回路５４で歪を歪み補償量として与えた後に、マスタ装置側デジタルアナログ変換回路として機能するデジタルアナログ変換回路５５でアナログ電気信号に変換され、光送信回路５６から光変調信号し、下り光信号としてリモート装置６１に出力される。 A digital radio modulation signal, which is a digital electric signal output from the digital radio modulation circuit 52 of the master device 51, is converted into an appropriate intermediate frequency band by a frequency conversion circuit 53 functioning as a frequency conversion circuit on the master device side, and a sampling rate conversion. After that, the precompensation circuit 54 gives distortion as a distortion compensation amount, and then the digital signal is converted into an analog electric signal by the digital-analog conversion circuit 55 functioning as a master device side digital-analog conversion circuit. Then, it is output to the remote device 61 as a downstream optical signal.

マスタ装置５１から送信された光変調信号である下り光信号は、光伝送路５８を伝送され、リモート装置６１へと入力される。リモート装置６１では、受信された光変調信号を光受信回路６２で電気信号に変換し、アナログデジタル変換回路６３でデジタル電気信号に変換される。 A downstream optical signal that is an optical modulation signal transmitted from the master device 51 is transmitted through the optical transmission path 58 and input to the remote device 61. In the remote device 61, the received optical modulation signal is converted into an electric signal by the optical receiving circuit 62, and converted into a digital electric signal by the analog / digital conversion circuit 63.

デジタル電気信号は補償回路６４で歪み量が補正された後、リモート装置側周波数変換回路として機能する周波数変換回路６５でサンプリングレート変換ならびにデジタル周波数変換された後にリモート装置側デジタルアナログ変換回路として機能するデジタルアナログ変換回路６６でアナログ電気信号に変換され、無線送信回路６７に入力され、無線信号として外部へ出力される。 After the distortion amount of the digital electric signal is corrected by the compensation circuit 64, the digital electric signal functions as a remote device side digital-analog conversion circuit after sampling rate conversion and digital frequency conversion by the frequency conversion circuit 65 that functions as a remote device side frequency conversion circuit. It is converted into an analog electrical signal by the digital / analog conversion circuit 66, input to the wireless transmission circuit 67, and output to the outside as a wireless signal.

このように、光伝送方法としてはアナログのＲＯＦを用いているが、光伝送で生じる非線形歪ならびに波形劣化を予補償回路５４または補償回路６４でのデジタル信号処理で補償することにより、高精度に無線信号を伝送することが可能となる。本実施形態においてデジタル無線変調回路５２から出力されるデジタル無線信号は、同相、直交成分に分離されたベースバンド信号および中間周波数帯信号のどちらでも構わない。 As described above, an analog ROF is used as the optical transmission method. However, the nonlinear distortion and waveform deterioration caused by the optical transmission are compensated by digital signal processing in the precompensation circuit 54 or the compensation circuit 64, thereby achieving high accuracy. Wireless signals can be transmitted. In this embodiment, the digital radio signal output from the digital radio modulation circuit 52 may be either a baseband signal or an intermediate frequency band signal separated into in-phase and quadrature components.

予補償回路５４は図５のように構成され、リモート装置６１の補償回路６４で検出される波形歪である歪み量を補正するように、歪演算部７１で入力信号に対して演算され、演算された歪み補償量を加算部７２が、デジタル無線変調回路が出力した信号に加算する。波形歪の要因としては、マスタ装置側デジタルアナログ変換回路として機能するデジタルアナログ変換回路５５の非線形歪、光送信回路５６の非線形歪、光伝送路５８での非線形歪、光受信回路６２の非線形歪、およびアナログデジタル変換回路６３の非線形歪がある。また、予補償回路５４の出力から補償回路６４の入力間の伝達関数に応じた波形予等化も予補償回路５４に等化器７３を配備し行う。 The pre-compensation circuit 54 is configured as shown in FIG. 5, and is calculated by the distortion calculation unit 71 so as to correct the distortion amount, which is the waveform distortion detected by the compensation circuit 64 of the remote device 61. The adder 72 adds the distortion compensation amount to the signal output from the digital radio modulation circuit. Causes of waveform distortion include nonlinear distortion of the digital-analog conversion circuit 55 that functions as a digital-analog conversion circuit on the master side, nonlinear distortion of the optical transmission circuit 56, nonlinear distortion in the optical transmission line 58, and nonlinear distortion of the optical reception circuit 62. And non-linear distortion of the analog-digital conversion circuit 63. In addition, an equalizer 73 is provided in the precompensation circuit 54 for waveform pre-equalization according to the transfer function between the output of the precompensation circuit 54 and the input of the compensation circuit 64.

伝達関数は、光送信回路５６の伝達関数、光伝送路５８の伝達関数および光受信回路６２の伝達関数の積となる。補償回路６４では、予補償回路５４と同様に図６に示すように、歪み量の検出および伝達関数の測定を行うとともに、マスタ装置側デジタルアナログ変換回路として機能するデジタルアナログ変換回路５５およびアナログデジタル変換回路６３のビット数等によって予補償回路５４で補償しきれない歪の補償を行うとともに波形等化を行う。 The transfer function is a product of the transfer function of the optical transmission circuit 56, the transfer function of the optical transmission path 58, and the transfer function of the optical reception circuit 62. As in the precompensation circuit 54, the compensation circuit 64 detects a distortion amount and measures a transfer function as shown in FIG. 6, and also has a digital-analog conversion circuit 55 and an analog-digital conversion functioning as a master device side digital-analog conversion circuit. Compensation for distortion that cannot be compensated by the pre-compensation circuit 54 is performed according to the number of bits of the conversion circuit 63, and waveform equalization is performed.

なお、補償回路６４で検出される歪や波形劣化が無線信号の品質にほとんど影響を与えない場合には、予補償回路５４および補償回路６４のどちらか一方の歪補償および波形等化機能を削除し、回路を簡単化することが可能である。 If the distortion or waveform deterioration detected by the compensation circuit 64 hardly affects the quality of the radio signal, the distortion compensation and waveform equalization functions of either the pre-compensation circuit 54 or the compensation circuit 64 are deleted. However, the circuit can be simplified.

このように予補償回路５４と補償回路６４で歪補償を行うことにより、大部分の歪み量は予補償回路５４で補償され、補償回路６４で補償する歪み量は小さくなるため、リモート装置６１の補償回路６４の回路規模の簡易化ならびに高精度な補償が可能となる。 Thus, by performing distortion compensation by the precompensation circuit 54 and the compensation circuit 64, most of the distortion amount is compensated by the precompensation circuit 54, and the distortion amount compensated by the compensation circuit 64 becomes small. The circuit scale of the compensation circuit 64 can be simplified and highly accurate compensation can be performed.

波形歪の検出については、リモート装置６１の補償回路６４に歪演算部７６を具備し、信号帯域外に出力される高次歪成分を検出することや特定周波数成分の位相回転を検出することで実現できる。具体的には、歪演算部７６で入力信号に対して演算され、演算された歪を歪補償量として、加算部７７が信号に加算する。また、等化器７８は、各入力間の伝達関数に応じた波形予等化を行う。 For the detection of waveform distortion, the compensation circuit 64 of the remote device 61 includes a distortion calculation unit 76 to detect higher-order distortion components output outside the signal band and to detect phase rotation of specific frequency components. realizable. Specifically, the distortion calculation unit 76 calculates the input signal, and the addition unit 77 adds the calculated distortion as a distortion compensation amount to the signal. The equalizer 78 performs waveform pre-equalization according to the transfer function between the inputs.

リモート装置６１のデジタルアナログ変換以降の無線送信回路６７での歪について、図７に示すように、無線送信回路６７が出力したデジタルアナログ電気信号をアナログデジタル変換し、歪検出部６９のデジタル信号処理で歪を検出し、リモート装置６１の補償回路６４で予補償することで実現可能である。 As for the distortion in the wireless transmission circuit 67 after the digital-analog conversion of the remote device 61, as shown in FIG. 7, the digital analog electric signal output from the wireless transmission circuit 67 is converted from analog to digital, and the digital signal processing of the distortion detector 69 is performed. This can be realized by detecting distortion and precompensating with the compensation circuit 64 of the remote device 61.

本実施形態でのマスタ装置５１の周波数変換回路５３でのデジタル周波数変換は、デジタル無線変調信号に式（１）で示すように周波数ｆ_０の搬送波を乗算することにより実現される（図８）。ｆ_０には、マスタ装置側デジタルアナログ変換回路として機能するデジタルアナログ変換回路５５のサンプリング周波数Ｆ_Ｓの１／２より低い周波数が用いられる。また、デジタル無線変調信号のサンプリング周波数は、デジタルアナログ変換回路５５のサンプリング周波数に変換される。

The digital frequency conversion in the frequency conversion circuit 53 of the master device 51 in the present embodiment is realized by multiplying the digital radio modulation signal by a carrier wave having a frequency f ₀ as shown in the equation (1) (FIG. 8). . The f _0, a frequency lower than half the sampling frequency F _S of the digital-to-analog converter 55 that functions as the master device side digital-to-analog converter circuit is used. In addition, the sampling frequency of the digital radio modulation signal is converted into the sampling frequency of the digital-analog conversion circuit 55.

本実施形態のリモート装置６１のリモート装置側周波数変換回路として機能する周波数変換回路６５のデジタル周波数変換は、アナログデジタル変換された電気信号からデジタルフィルタでデジタル無線変調信号成分を抽出した後、式（２）で示される周波数ｆ_ａの搬送波を乗算することで実現される。

The digital frequency conversion of the frequency conversion circuit 65 functioning as the remote device side frequency conversion circuit of the remote device 61 of the present embodiment is obtained by extracting a digital wireless modulation signal component from the analog-digital converted electric signal with a digital filter, This is realized by multiplying the carrier wave of frequency f _a shown in 2).

ここで、周波数ｆ_ａを次式で与えられる周波数に選ぶと、式（３）で示される。

Here, when selecting the frequency f _a to the frequency given by the following equation, represented by the formula (3).

デジタルアナログ変換されたアナログ電気信号のＮ番目の高調波成分を無線送信回路６７のバンドパスフィルタで抽出することにより無線周波数の信号となる（図９）。上式において、ｆ_ｃは無線搬送波周波数、Ｎはｆ_Ｃ／Ｆ_Ｓを超えない最大の整数である。 A N-th harmonic component of the analog electric signal that has been converted from digital to analog is extracted by a band-pass filter of the wireless transmission circuit 67 to become a radio frequency signal (FIG. 9). In the above equation, f _c is the radio carrier frequency, and N is the largest integer that does not exceed f _C / F _S.

高調波成分の電力はＮが大きくなると減衰していくため、より柔軟に無線搬送波周波数を設定する場合、ｆ_Ｃを中間周波数として、無線送信回路６７のミキサで周波数ｆ_２の局部発振と混合し、さらに別の周波数に変換することも可能である（図１０）。 Since the power of the harmonic component attenuates as N increases, when setting the radio carrier frequency more flexibly, f _C is set as the intermediate frequency and mixed with the local oscillation of the frequency f _{2 by} the mixer of the radio transmission circuit 67. It is also possible to convert to another frequency (FIG. 10).

このように周波数変換を行う場合、無線周波数の搬送波周波数精度がサンプリング周波数精度に依存するため、マスタ装置５１とリモート装置６１間で周波数を正確に合わせておく必要がある。マスタ装置５１のマスタ装置側周波数変換回路として機能する周波数変換回路５３で基準クロックを重畳し、リモート装置６１のリモート装置側周波数変換回路として機能する周波数変換回路５３で基準クロックを抽出し、デジタルアナログ変換することにより基準クロックを転送することが可能である。 When performing the frequency conversion in this way, since the carrier frequency accuracy of the radio frequency depends on the sampling frequency accuracy, it is necessary to accurately match the frequency between the master device 51 and the remote device 61. The reference clock is superimposed by the frequency conversion circuit 53 functioning as the master device side frequency conversion circuit of the master device 51, the reference clock is extracted by the frequency conversion circuit 53 functioning as the remote device side frequency conversion circuit of the remote device 61, and digital analog It is possible to transfer the reference clock by converting.

初期状態においてリモート装置６１のサンプリング周波数がマスタ装置５１に対してずれている場合においても、リモート装置６１側のサンプリングクロックでアナログデジタル変換とデジタルアナログ変換を行うため、周波数誤差の影響を受けずに基準クロックを再生することができる（図１１）。 Even when the sampling frequency of the remote device 61 is deviated from the master device 51 in the initial state, analog-to-digital conversion and digital-to-analog conversion are performed with the sampling clock on the remote device 61 side. The reference clock can be recovered (FIG. 11).

このため、図１２に示すように、抽出された基準クロックにリモート装置の基準クロックを位相同期ループ（ＰＬＬ７０：Ｐｈａｓｅ−ＬｏｃｋｅｄＬｏｏｐ）で同期させることにより、マスタ装置５１とリモート装置６１の間で周波数同期をとることができ、無線周波数を安定に出力することができる。 For this reason, as shown in FIG. 12, the reference clock of the remote device is synchronized with the extracted reference clock by a phase-locked loop (PLL70), so that the frequency between the master device 51 and the remote device 61 is increased. Synchronization can be achieved and the radio frequency can be output stably.

また、マスタ装置５１の基準クロックを安定なクロックとし、リモート装置６１のＰＬＬ７０のループフィルタを狭帯域なフィルタとすることにより、サンプリングクロックのジッタが低減され、高精度な無線信号を出力することが可能となる。 Further, by using a stable clock as the reference clock of the master device 51 and a narrow band filter as the loop filter of the PLL 70 of the remote device 61, the jitter of the sampling clock can be reduced and a highly accurate radio signal can be output. It becomes possible.

本実施形態の光送受信回路の帯域幅は、マスタ装置５１のデジタルアナログ変換回路出力５５での無線信号が透過できる帯域幅があれば十分である。例えば、ＬＴＥ−Ａのキャリアアグリゲーションで１００ＭＨｚの帯域が必要な場合、ｆ_Ｃを１００ＭＨｚ程度としても２００ＭＨｚ程度の帯域があれば十分であり、汎用の通信用半導体レーザを光源とした直接変調で送信可能である。 The bandwidth of the optical transmission / reception circuit of the present embodiment is sufficient if there is a bandwidth that allows radio signals to pass through the digital-analog conversion circuit output 55 of the master device 51. For example, when LTE-A carrier aggregation requires a 100 MHz band, even if f _{C is set} to about 100 MHz, a band of about 200 MHz is sufficient, and transmission is possible by direct modulation using a general-purpose communication semiconductor laser as a light source. It is.

また、光受信回路６２についても数百ＭＨｚ帯域の廉価な部品の使用が可能である。デジタルアナログ変換およびアナログデジタル変換のサンプリング周波数については最大でも５００ＭＨｚ程度であるため、低価格で１４ビット以上の高精度な部品が使用可能である。 Also, the optical receiver circuit 62 can use inexpensive parts in the several hundred MHz band. Since the sampling frequency of the digital / analog conversion and the analog / digital conversion is about 500 MHz at the maximum, it is possible to use a high-precision component of 14 bits or more at a low price.

リモート装置６１の監視制御信号は、マスタ装置５１のマスタ装置側監視制御回路として機能する監視制御回路５７から周波数変換回路５３において無線変調信号に多重されて光伝送路５８を伝送され、リモート装置６１のリモート装置側周波数変換回路として機能する周波数変換回路６５で無線変調信号と分離されて監視制御回路６８に入力される。 The monitoring control signal of the remote device 61 is multiplexed with the radio modulation signal in the frequency conversion circuit 53 from the monitoring control circuit 57 functioning as the master device side monitoring control circuit of the master device 51 and transmitted through the optical transmission line 58. The frequency conversion circuit 65 functioning as a remote device side frequency conversion circuit is separated from the wireless modulation signal and input to the monitoring control circuit 68.

本実施形態で転送する監視制御情報としては、リモート装置６１の設定・制御に関する情報、無線信号に関する情報、補償回路６４に関する情報等がある。データレートとしては１００ｋｂ／ｓ〜１Ｍｂ／ｓ程度あれば十分であり、適当な搬送波周波数で位相変調等を行い、マスタ装置５１からリモート装置６１まで転送する。低速度であるため、信号電力を抑えることができ、無線信号への干渉は十分低いレベルにまで低減することが可能である。 The monitoring control information transferred in the present embodiment includes information related to setting / control of the remote device 61, information related to a radio signal, information related to the compensation circuit 64, and the like. A data rate of about 100 kb / s to 1 Mb / s is sufficient. Phase modulation or the like is performed at an appropriate carrier frequency, and the data is transferred from the master device 51 to the remote device 61. Since the speed is low, signal power can be suppressed, and interference with a radio signal can be reduced to a sufficiently low level.

本発明は情報通信産業に適用することができる。 The present invention can be applied to the information communication industry.

１１、３１：無線変復調部
１２、３２：無線変復調回路
１３、１５、３３、３５：光インタフェース
１４、３４：光ファイバ伝送路
１６、３６：無線送受信回路
２１、４１：無線送受信部
５１：マスタ装置
５２：デジタル無線変調回路
５３、６５：周波数変換回路
５４：予補償回路
５５、６６：デジタルアナログ変換回路
５６：光送信回路
５７、６８：監視制御回路
５８：光伝送路
６１：リモート装置
６２：光受信回路
６３：アナログデジタル変換回路
６４：補償回路
６７：無線送信回路
６９：歪検出部
７０：ＰＬＬ
７１、７６：歪演算部
７２、７７：加算部
７３、７８：等化器 11, 31: Radio modulation / demodulation unit 12, 32: Radio modulation / demodulation circuits 13, 15, 33, 35: Optical interface 14, 34: Optical fiber transmission line 16, 36: Radio transmission / reception circuit 21, 41: Radio transmission / reception unit 51: Master device 52: Digital radio modulation circuit 53, 65: Frequency conversion circuit 54: Precompensation circuit 55, 66: Digital analog conversion circuit 56: Optical transmission circuit 57, 68: Supervisory control circuit 58: Optical transmission path 61: Remote device 62: Optical Reception circuit 63: Analog-digital conversion circuit 64: Compensation circuit 67: Wireless transmission circuit 69: Distortion detection unit 70: PLL
71, 76: Distortion calculation units 72, 77: Addition unit 73, 78: Equalizer

Claims

Adding a distortion compensation amount calculated in advance to an electrical signal, converting the added electrical signal into a downstream optical signal, and transmitting the downstream optical signal to a remote device connected via an optical transmission path;
The downstream optical signal transmitted by the master device is received, the received downstream optical signal is converted into an electrical signal, the amount of distortion of the electrical signal is detected, the detected amount of distortion is compensated, and the compensated electrical A remote device that converts the signal into a wireless signal and outputs it externally;
Equipped with a,
The master device is
A digital radio modulation circuit that outputs a digital electrical signal;
A master device-side frequency conversion circuit that converts the digital electrical signal into a predetermined intermediate frequency band and converts the sampling rate;
A precompensation circuit for adding a distortion compensation amount calculated in advance to the digital electrical signal converted by the master device side frequency conversion circuit;
A digital-analog conversion circuit on the master device side that converts the digital electrical signal to which the distortion compensation amount is added into an analog electrical signal; and
An optical transmission circuit for optically modulating the analog electrical signal and transmitting the optically modulated optical signal as the downstream optical signal;
Wireless signal transmission system according to claim comprise a.

The master device is
It further includes a master device side monitoring control circuit that outputs a pre-generated monitoring control signal to the master device side frequency conversion circuit,
It said master device side frequency conversion circuit, a radio signal transmission system according to claim 1, characterized in you multiple possible pre Symbol monitoring control signal to a digital electric signal the digital radio modulation circuit is output.

Adding a distortion compensation amount calculated in advance to an electrical signal, converting the added electrical signal into a downstream optical signal, and transmitting the downstream optical signal to a remote device connected via an optical transmission path;
The downstream optical signal transmitted by the master device is received, the received downstream optical signal is converted into an electrical signal, the amount of distortion of the electrical signal is detected, the detected amount of distortion is compensated, and the compensated electrical A remote device that converts the signal into a wireless signal and outputs it externally;
Equipped with a,
The remote device is:
An optical receiver circuit that receives the downstream optical signal transmitted by the master device and converts it into an analog electrical signal;
An analog-digital conversion circuit that converts the analog electrical signal converted by the optical receiver circuit into a digital electrical signal;
Compensation for detecting the distortion compensation amount of the digital electric signal added by the pre-compensation circuit included in the master device, detecting a distortion amount other than the distortion compensation amount, and compensating the detected distortion compensation amount and the distortion amount. Circuit,
A remote device side frequency conversion circuit for outputting the distortion compensation amount and the digital electric signal compensated for the distortion amount;
A remote device side digital-analog conversion circuit for converting the digital electric signal output by the remote device side frequency conversion circuit into an analog electric signal;
A wireless transmission circuit that converts the analog electrical signal converted by the digital analog conversion circuit on the remote device side into a wireless signal and outputs the wireless signal;
Wireless signal transmission system according to claim comprise a.

Before Symbol remote device,
A remote device side monitoring control circuit is further provided,
The remote device side frequency conversion circuit, wherein the extracting multiplexed monitored control signals at the master device side frequency conversion circuit comprising a master device, and outputs the extracted the monitoring control signal to the remote device-side monitoring and control circuit,
The remote device side monitoring and control circuit, the radio signal transmission system according to claim 3, wherein the setting change and control intends row of the remote device in response to the monitor control signal.

A digital radio modulation circuit that outputs a digital electrical signal;
A master device-side frequency conversion circuit that converts the digital electrical signal into a predetermined intermediate frequency band and converts the sampling rate;
A precompensation circuit for adding a distortion compensation amount calculated in advance to the digital electrical signal converted by the master device side frequency conversion circuit;
A digital-analog conversion circuit on the master device side that converts the digital electrical signal to which the distortion compensation amount is added into an analog electrical signal; and
An optical transmission circuit that optically modulates the analog electrical signal and transmits the optically modulated downstream optical signal;
A master device comprising:

Further comprising a master apparatus monitoring control circuit for outputting a supervisory control signal generated Me pre to the master device side frequency conversion circuit,
6. The master device according to claim 5 , wherein the master device-side frequency conversion circuit multiplexes the monitoring control signal with a digital electric signal output from the digital radio modulation circuit.

An optical receiving circuit that receives the downstream optical signal transmitted by the master device and converts it into an analog electrical signal;
An analog-digital conversion circuit that converts the analog electrical signal converted by the optical receiver circuit into a digital electrical signal;
Compensation for detecting the distortion compensation amount of the digital electric signal added by the pre-compensation circuit included in the master device, detecting a distortion amount other than the distortion compensation amount, and compensating the detected distortion compensation amount and the distortion amount. Circuit,
A remote device side frequency conversion circuit for outputting the distortion compensation amount and the digital electric signal compensated for the distortion amount;
A remote device side digital-analog conversion circuit for converting the digital electric signal output by the remote device side frequency conversion circuit into an analog electric signal;
A wireless transmission circuit that converts the analog electrical signal converted by the digital analog conversion circuit on the remote device side into a wireless signal and outputs the wireless signal;
A remote device comprising:

Further comprising a remote device side monitoring control circuit,
The remote device side frequency conversion circuit extracts the monitoring control signal multiplexed by the master device side frequency conversion circuit included in the master device, and outputs the extracted monitoring control signal to the remote device side monitoring control circuit,
8. The remote device according to claim 7 , wherein the remote device-side monitoring control circuit performs setting change and control of the remote device in accordance with the monitoring control signal.

Master device adds the distortion compensation amount calculated in advance into an electric signal, converts the electrical signal obtained by adding the downstream optical signal, an optical signal that transmits the downstream optical signal through the optical transmission path to the remote device Sending procedure,
It said remote device, as well as receiving the downlink optical signal in which the master device transmits, to convert the downstream optical signal received into an electrical signal, detects the distortion amount of the electric signal, based on the detected amount of strain A wireless signal output procedure for adding the distortion compensation amount calculated in the above to the electrical signal to compensate for the distortion amount, converting the compensated electrical signal into a wireless signal and outputting the signal to the outside;
In order ,
The master device is
A digital radio modulation procedure for outputting a digital electrical signal;
A master device side frequency conversion procedure for converting the digital electrical signal into a predetermined intermediate frequency band and converting the sampling rate;
A pre-compensation procedure for adding a distortion compensation amount calculated in advance to the digital electrical signal converted by the master device-side frequency conversion procedure;
A digital-analog conversion procedure on the master device side that converts the digital electrical signal to which the distortion compensation amount is added into an analog electrical signal;
An optical transmission procedure for optically modulating the analog electrical signal and transmitting the optically modulated optical signal as the downstream optical signal;
Transmission method for a wireless signal transmission system according to claim to run.

Master device adds the distortion compensation amount calculated in advance into an electric signal, converts the electrical signal obtained by adding the downstream optical signal, an optical signal that transmits the downstream optical signal through the optical transmission path to the remote device Sending procedure,
It said remote device, as well as receiving the downlink optical signal in which the master device transmits, to convert the downstream optical signal received into an electrical signal, detects the distortion amount of the electric signal, based on the detected amount of strain A wireless signal output procedure for adding the distortion compensation amount calculated in the above to the electrical signal to compensate for the distortion amount, converting the compensated electrical signal into a wireless signal and outputting the signal to the outside;
In order ,
The remote device is
An optical reception procedure for receiving the downstream optical signal transmitted by the master device and converting it into an analog electrical signal;
An analog-to-digital conversion procedure for converting the analog electrical signal converted by the optical reception procedure into a digital electrical signal;
A distortion compensation amount of the digital electric signal added in the pre-compensation procedure executed by the master device is detected, and a distortion amount other than the distortion compensation amount is detected, and the detected distortion compensation amount and the distortion amount are compensated. Compensation procedures;
Remote apparatus side frequency conversion procedure for outputting the distortion compensation amount and the digital electric signal compensated for the distortion amount;
A remote device-side digital-analog conversion procedure for converting the digital electrical signal output in the remote device-side frequency conversion procedure into an analog electrical signal;
A wireless transmission procedure for converting the analog electrical signal converted by the digital analog conversion procedure on the remote device side into a wireless signal and outputting it to the outside;
Transmission method for a wireless signal transmission system according to claim to run.