移动通信在多功能远程医疗保健系统中的应用——通信工程类毕业设计中英文翻译、外文翻译

移动通信在多功能远程医疗保健系统中的应用
摘要：
本论文主要研究方向是对远程医疗和家庭监测提供有效的紧急措施。

可能出现紧急病例的场所很多，常见的有救护车，乡村卫生所及其它偏远医疗场所，比如船在广阔的海面航行时也是一个很普通的可能的紧急医疗场所的例子，不过我们监测的重点是医疗遥感监测和家庭远程医疗。

为了满足上述不同领域的发展需求，我们设计了一个兼具实时、储存和转送功能的设备，该设备由一个基本单元和一个远程医疗单元组成。

一个完整的系统可以用于在救护车、乡村卫生所和轮船上处理紧急医疗事故，只需在紧急情况处安装一个可移动的远程医疗单元，而在医院专家处安装一个基本单元；还可加强重病特别护理的防范工作，给重点护理组的医生安装一个基本可移动单元，同时远程医疗单元仍在重点护理病人所在地，这样就可实现对家庭的无线监测，通过安装远程医疗单元在病人的家里，而基本单元在医院或者是医生的办公室。

该系统可传输重要的生物信号包括病人的肖像。

而传输工作可通过GSM移动网络系统、卫星连接系统或那些较清晰的旧式电话系统进行。

用这个装置，在处理突发事故或远程医疗事故时，一个专业医生通过信息处理可以“移动”到病人所在地，从而指导非专业人员。

为了保护和存储在远程医疗过程中相互交换的所有数据，我们又开发了一个咨询单元，使用多媒体资料库存储和管理系统收集的数据。

该系统技术上已被多个无线电通讯方法所检测，另外它已在三个不同国家临床试验，使用的是标准医学协议。

背景
远程医疗就是卫生保健的传递及一段距离内使用无线电通信手段实现医学知识的共享。

所以，远程医疗的目的是为了给人手不足的偏远地区提供专家级的卫生保健，通过现代化通信和信息知识提供先进的紧急医疗措施。

远程医疗的概念是大约30年前随着一些现在很普通的技术，比如电话、传真机等提出的。

目前，远程医疗系统包括的工艺技术有交互式视频、高清晰度监视器、高速互联网和交换系统及高速无线电通信含纤维光学和卫星。

实时又专业化的医学治疗可以很大地提高人手不足的乡村、偏远地区的卫生保健服务。

有效的突发病例远程医疗措施和家庭监测方案是我们这个课题主要讨论的范
围。

在很多各种各样的研究里，这个课题都是至关重要的。

尽管救护车、乡村卫生所还有航海的轮船都可能发生紧急病例，但我们监测的重点是医疗遥感勘测和后来的远程家庭医疗。

在紧急病例中必须进行立即治疗，最近的调查表明入院前早期而又专业化的病人护理有利于病人的存活，尤其是严重的头部损伤、脊髓和内脏损伤，为了病人以后的康复，处理病人的手段至关重要。

我们可以看看过去的车辆事故统计：在1997年，美国报道的6753500事故中有42000人丧身，2182660个司机，1125890个乘客受伤；欧洲同样时期有50000个人因撞车而丧身，而50万人严重受伤；另外1997年，在希腊一个国家有高达1/3的人是因撞车而死，2500个致命伤害中77.4﹪受伤时远离有能力的卫生保健机构，所以耗费了很长一段时间。

此外，同样的调查表明66﹪的死者是在死前最近的24小时丧身的。

减小这种事故的死亡率是完全可能的，可通过采用一些病人可更好地进行院前护理、监测的方法和策略。

疗养监测也可解决病人突发情况，重点就在于医院对重点护理组的病人进行持续的监控，同时把监控信息随时随地传给能够胜任的医生。

这样，负责的医生就的24小时掌握病人情况，即使不在场时也可通过先进的无线电通信手段提供重要的咨询，换句话说，视频监控是完全可行的。

方法
远程医疗系统的发展趋势
由上所述，本论文的研究范围是设计并实现一个综合的医疗系统，该系统可以处理不同距离医疗系统的需要，尤其表现在以下几方面：
●给救护车，乡村卫生所（或其他偏远的卫生机构）和航海的轮船提供紧急医疗措
施
●实现对重点护理病人的监测
提供家庭护理，尤其是那些遭受慢性或永久性疾病的人（像心脏病），换句话说，我们研究的多功能系统由两个主要部分组成：
a.远程医疗单元（它可以是手提式电脑或其它）
基本单元或医生单元（它也可是手提式电脑或其它，一般都位于中心医院里面图一描述了系统的总体体系机构，系统的每个不同的应用即远程医疗单元位于病人所在处，而基本单元（或是叫医生单元）即接收和监测病人的生理信号及肖像处。

远程医疗装置负责收集病人的资料（生理信号和肖像），然后自动把检测到的信号传送到基本单元。

基本单元由一组用户指令软件组成，运用这套指令可以接收远程医疗装置的资料、反馈信息及把重要信息存储在地方资料室。

该系统应用很广泛(每次只须稍作改变），可满足现代卫生保健的发展需求。

在系统技术实现以前，上述远程医疗系统应用的总设想应根据目前的发展趋势和需求而制定，只有这样，在设计和发展过程中，才能把诸多因素都考虑进去，所以才能在任何环境和情形下达到最大的适用性和可用性。

表一提供了这个总思路的结构，，同时兼顾了一系列可影响远程医疗的标准（如价格、轻便性、自治性、装置的重量和大小、计算机、摄像机的类型和质量、所采用的通讯方法），除此之外远程医疗的应用还可通过其它标准检验，像安全需要，传输类型（连续地存储和转送），心电图要求等。

这些在系统总体技术描述中将作详细说明。

系统设计和技术实现
由上述可知，系统由两个独立模块组成（图一）：a)一个位于病人所在地，叫做远程医疗单元。

b)另一个位于医生所在地，叫做基本单元。

医生在紧急病例或检测一个偏远地方病人时可使用该系统。

系统的设计和实现都建立在对用户要求的详细分析和对系统功能的具体反应的基础上。

而研究主要以远程医疗项目所经历的过程为基础，像救护车和急救112，它们使用远程医疗功能性装置的功能原型已经建立了，且通过了初步评估。

通过这些具体实践，我们已经定相了解了实现远程医疗装置的需要，这将进一步促进我们形成一个灵活的体系结构，可用于需要信息传输的紧急病例或者是监测病例。

远程医疗单元负责从易发地带收集和传输生理信号和病人的肖像，而医生单元负责接收和显示输入数据。

两个场所间的信息流（分层描述）如图二所示。

a)远程医疗单元
远程医疗单元主要包括四个模块，生理信号获得模块，负责接收生理信号；数
码相机模块负责捕获图像；处理部件大多是私人计算机；通讯模块（GSM、卫星或光学地面模拟器）。

所收集的病人生理信号（然后传送到基本单元）主要有：
●心电图，由病人所用的监视器决定
●心跳率
●无入侵血压
●入侵血压
●体温
●肺活量
所使用的计算机由远程应用的类型决定（远程医疗单元所发挥的作用），如表一所示，a)要求系统自动化，形状小的，一台像东芝，100ct的笔记本电脑即可，较轻便的机器装置如图3所示。

b)要求半自动，大小不限的，采用典型的奔腾处理机即可。

c)而那些不要求自动化，轻便及大小的，一般的台式机即可选用。

远程医疗单元的控制是完全自动化的。

远程医疗单元用户要做的仅仅是把生理信号检测器连接到病人，然后打开计算机。

计算机将自动连接到基本单元。

尽管基本单元几乎控制了系统的所有操作，远程医疗单元用户仍需掌握一部分操作指令，这样当系统处于偏远卫生所或轮船上时，两个地方的人就可对话了。

b)基本单元（或医生单元）
基本单元主要由一台接有调制解调器的精密计算机组成，它的作用主要是负责数据交换。

另外，基本单元的计算机还负责显示远程医疗单元的输入信号。

当一个专家使用医院以外的基本单元时，比如在重病特别护理病房，由图一用一台GSM的笔记本电脑或一台装有POTS调制解调的台式机就可。

而当基本单元位于医院里时，只需一台连接到医院信息网络并装有POTS调制解调的台式机。

专家们就可把它作为一个处理终端。

通过基本单元，用户可以完全控制远程医疗端。

用户还能够监测与客户端（远程医疗单元）的连接状态，发送像图四那样的操作模式（生理信号和图像）到远程医疗
单元。

只要基本单元连接到医院局域网，用户可选择连接到任何一个远程医疗单元，如图五所示基本单元的入网用户可以选择连接到任何一个远程医疗单元，入网单元可以是重点护理组的远程医疗单元或通过电话线上网的远距离移动用户单元。

基本单元用户可以监测来自远程医疗端的生理或图像信号，而且也能够一直与病人进行交谈。

该单元可完全控制远程医疗部分。

医生可以发送所有可能的命令来获取图像和生理信号，图6显示了一个典型的生理信号接收窗口（持续操作）。

当系统操作图像模块时，医生可以在图像上加些注解，然后把加注解后的图像发送到远程医疗端，远程医疗端的用户也可以把接收到的信息再加上注解，然后反馈回基本单元处。

当系统操作生理信号模块时（如图6所示），对重要生理信号的传输方法有两种，连续传输、储存和转送传输的方法。

采用什么方法取决于所传输的心电图的波形通道和无线通路的数据传输率。

持续操作时，基本端用户可以向远程医疗监测端发送指令对波形进行测量，如血压；用户也可暂停输入心电图。

c)技术约束—可行性
生理信号传输
不仅是生理信号，监测的信息像警铃或监测到的状况也需从远程医疗端传输到基本端，ECG波形和SPO2或CO2波形（若可获得）是连续的传输信号。

对所有的监测器，ECG数据以10bits/样品或12bits/样品进行采样，采样率是200样品/s，所以对一个ECG通道相当于是2000bits/s或2400bits/s.SPO2或CO2 波形是以10bits/样品取样，取样率是100样品/s，所以一个通道就是1000bits/s。

最新监测数据是以1次/s进行刷新，所以传输少量数据大约可以达到200bits/s,系统使用的所有监测器可以提供收集到的信号的数字输出量。

图像传输
远程医疗端数码相机所能捕获的图像是320*240像素，采用的是JPEG进行压缩，最终数据大约是5-6kB，取决于使用JPEG的压缩率。

传输率
信号是通过GSM、卫星或POTS传输的。

系统技术测试使用的GSM网络，目前允许的数据传输率达到了9600bps（但处于正常的操作状态下），使用高速环绕交换数据时可达到43200bps.卫星连接传输率取决于仪器和卫星系统的使用场合；大概范围是2400bps到64000bps。

使用不同种类的卫星系统会增加仪器的价钱和用户的开销。

像我们这种情况使用INMARAS电话系统即可，而数据传输率仅仅是2400bps，但仪器便宜，开销少。

POTS可以达到的数据传输率是56000bps，所以它能够支持连续而又快速的信息传输（如表二所示）。

通过无线通讯传输实际所能达到的数据传输率从来不会超过理论值，而实际数据传输率取决于系统使用的地区和时间。

传输生理信号有两种方法实时传输，连续地将信号从客户端传输到家服务器；储存和转发传输，信号提前获得并储存在客户端，然后作为文件传输给服务器。

采取什么方法主要取决于所使用的无线电通讯的最大数据传输率和不同情况下生理信号监测器的数字输出量。

最后的结果是 " 多功能" 电子医疗系统,是一个能在不同的应用领域中被采用的灵活的体系结构，该系统已通过了很多医疗设备和无线通信设备的试验。

本论文所针对的对象是乡村卫生所、救护车或航海的轮船。

数据传输使用的是TCP/IP网络协议，网络传输数据使用TCP/IP协议简单且容易，又具有高带宽、低误码率。

要传输n字节的数据块，使用TCP/IP协议，需在报头另加55字节。

在传输少量数据的情况下，这加额外增加大量数据（例如，当传输10 字节时，网络将自动增加至65字节）。

当传输的数据流大小大于最大允许的传输单元时，这个数据流将分裂成几个较小的数据包，每个包都和允许的最大传输单元一样大，而达到目的地时，所有分裂的包将会重新连接；如果其中分裂的任何一个包丢失，将会引起严重错误。

考虑到数据传输的上述两种情况，尤其是那种低带宽、高差错率的网络（像GSM 移动网络和卫星连接）。

采用一种充分利用带宽的方法，使传输的数据要么充分大，要么充分小。

为了测量使用GSM网络时TCP/IP的执行，对不同大小的数据块进行测试，该测试使用的是GSM调制解调器，NOKIA2.0电话卡。

进行试验时，选择了从71到479字节的数据包，数据包的大小与发送的数据率成正比，发送时使用串口RS232 。

数据
包的大小依次有7.95.143.239.287.335.383.431.455.479字节。

由上所述，图8是对数据传输的测量。

我们对要选择的数据块大小的要求是：不给传输数据加过长的报头，不会引起数据传输的分块，不会给信号的传输引起很大的时延。

经多方面考虑，我们选择的数据块大小是431字节。

结论
我们已经开发了适于远程医疗应用的医疗产品，该装置使用GSM移动电话连接，卫星连接或POTS连接，允许收集和传输生理信号、病人的肖像，具有双向视频功能。

在接收数据和与专家交谈时，允许用户在可自由模式下操作，这种先进的人为控制界面提高了系统的功能性。

为了在日常健康预防中介绍该系统，通过使用一个可控制的医疗协议系统已被临床试验。

目前，该系统已经在两个不同国家，希腊和塞浦路斯安装且正在使用。

据现在的发展情形可以看出系统很有前景，所以为满足未来需求，激励着我们不断发展和提高该系统。

Multi-purpose HealthCare Telemedicine Systems with mobile communication link support
E Kyriacou*1,2, S Pavlopoulos1, A Berler1, M Neophytou1, A Bourka1,
A Georgoulas1, A Anagnostaki1, D Karayiannis3, C Schizas2, C Pattichis2,A Andreou2 and D Koutsouris1
abstract
The provision of effective emergency telemedicine and home monitoring solutions are the major fields of interest discussed in this study. Ambulances, Rural Health Centers (RHC) or other remote health location such as Ships navigating in wide seas are common examples of possible emergency sites, while critical care telemetry and telemedicine home follow-ups are important issues of telemonitoring. In order to support the above different growing application fields we created a combined real-time and store and forward facility that consists of a base unit and a telemedicine (mobile) unit. This integrated system: can be used when handling emergency cases in ambulances, RHC or ships by using a mobile telemedicine unit at the emergency site and a base unit at the hospital-expert's site, enhances intensive health care provision by giving a mobile base unit to the ICU doctor while the telemedicine unit remains at the ICU patient site and enables home telemonitoring, by installing the telemedicine unit at the patient's home while the base unit remains at the physician's office or hospital. The system allows the transmission of vital biosignals (3–12 lead ECG, SPO2, NIBP, IBP, Temp) and still images of the patient. The transmission is performed through GSM mobile telecommunication network, through satellite links (where GSM is not available) or through Plain Old Telephony Systems (POTS) where available. Using this device a specialist doctor can telematically "move" to the patient's site and instruct unspecialized personnel when handling an emergency or telemonitoring case. Due to the need of storing and archiving of all data interchanged during the telemedicine sessions, we have equipped the consultation site with a multimedia database able to store and manage the data collected by the system. The performance of the system has been technically tested over several telecommunication means; in addition the system has been clinically validated in three different countries using a standardized medical protocol.
Background
Telemedicine is defined as the delivery of health care and sharing of medical knowledge over a distance using telecommunication means. Thus, the aim of Telemedicine is to provide expert-based health care to understaffed remote sites and to provide advanced
emergency care through modern telecommunication and information technologies. The concept of Telemedicine was introduced about 30 years ago through the use of nowadays-common technologies like telephone and facsimile machines. Today, Telemedicine systems are supported by State of the Art Technologies like Interactive video, high resolution monitors, high speed computer networks and switching systems, and telecommunications superhighways including fiber optics, satellites and cellular telephony [1].
The availability of prompt and expert medical care can meaningfully improve health care services at understaffed rural or remote areas. The provision of effective emergency Telemedicine and home monitoring solutions are the major fields of interest discussed in this study. There are a wide variety of examples where those fields are crucial. Nevertheless, Ambulances, Rural Health Centers (RHC) and Ships navigating in wide seas are common examples of possible emergency sites, while critical care telemetry and Telemedicine home follow-ups are important issues of telemonitoring. In emergency cases where immediate medical treatment is the issue, recent studies conclude that early and specialized pre-hospital patient management contributes to the patient's survival [2]. Especially in cases of serious head injuries, spinal cord or internal organs trauma, the way the incidents are treated and transported is crucial for the future well being of the patients.
A quick look to past car accident statistics points out clearly the issue: During 1997, 6753500 incidents were reported in the United States [3] from which about 42000 people lost their lives, 2182660 drivers and 1125890 passengers were injured. In Europe during the same period 50000 people died resulting of car crash injuries and about half a million were severely injured. Furthermore, studies completed in 1997 in Greece [4], a country with the world's third highest death rate due to car crashes, show that 77,4 % of the 2500 fatal injuries in accidents were injured far away from any competent healthcare institution, thus resulting in long response times. In addition, the same studies reported that 66% of deceased people passed away during the first 24 hours.
The reduction of all those high death rates is definitely achievable through strategies and measures, which improve access to care, administration of pre-hospital care and patient monitoring techniques.Critical care telemetry is another case of handling emergency situations. The main point is to monitor continuously intensive care units' (ICU) patients at a hospital and at the same time to display all telemetry information to the competent doctors anywhere, anytime [14]. In this pattern, the responsible doctor can be informed about the patient's condition at a 24-hour basis and provide vital consulting even if he's not physically present. This is feasible through advanced telecommunications means or in other words via Telemedicine.
Methods
Trends and needs of Telemedicine systems
As mentioned above, scope of this study was to design and implement an integrated Telemedicine system, able to handle different Telemedicine needs especially in the fields of:
• Emergency health care provision in ambulances, Rural Hospital Centers (or any other remote located health center) and navigating Ships
• Intensive care patients monitoring
• Home telecare, especially for patients suffering from chronic and /or perma nent diseases (like heart disease).
In other words we determined a "Multi-purpose" system consisting of two major parts: a) Telemedicine unit (which can be portable or not portable depending on the case) and b) Base unit or doctor's unit (which can be portable or not portable depending on the case and usually located at a Central Hospital).
Figure 1 describes the overall system architecture. In each different application the Telemedicine unit is located at the patient's site, whereas the base unit (or doctor's unit) is located at the place where the signals and images of the patient are sent and monitored. The Telemedicine device is responsible to collect data (biosignals and images) from the patient and automatically transmit them to the base unit. The base unit is comprised of a set of user-friendly software modules, which can receive data from the Telemedicine device, transmit information back to it and store important data in a local database. The system has several different applications (with small changes each time), according to the current healthcare provision nature and needs.
Before the system's technical implementation, an overview of the current trends and needs in the aforementioned Telemedicine applications was made, so that the different requirements are taken into account during design and development, thus ensuring
maximum applicability and usability of the final system in distinct environments and situations. Table 1 provides the results of this overview, which was done towards a predefined list of criteria that usually influence a Telemedicine application implementation (cost, portability, autonomy, weight and size of Telemedicine device, type and quality of PC and camera, communication means used). Besides the above, the Telemedicine applications can be examined towards other criteria, like for example security needs, transmission type (continuos, store & forward) needs, ECG leads required (3 or 12 leads), etc. These last are examined in more detail in the next paragraph, where the overall technical description of the system is provided.
System design and technical implementation
As mentioned above, the system consists of two separate modules (Figure 1): a) the unit located at the patient's site called "Telemedicine unit" and b) the unit located at doctor's site called "Base Unit". The Doctor might be using the system either in an Emergency case or when monitoring a patient from a remote place.
The design and implementation of the system was based on a detailed user requirements analysis, as well as the corresponding system functional specifications. The study was mainly based on the experience of Telemedicine projects named AMBULANCE [22] and Emergency 112 [33] where functional prototypes of a device with emergency Telemedicine functionalities was built and extensively evaluated. Through these project we had phased the need to implement a telemedicine device, which would facilitate a flexible architecture and could be used in several emergency or monitoring cases that have simiral needs of information transmition.
The Telemedicine unit is responsible for collecting and transmitting biosignals and still images of the patients from the incident place to the Doctor's location while the Doctor's unit is responsible for receiving and displaying incoming data. The information flow (using a layered description) between the two sites can be seen in Figure 2.
a) Telemedicine Unit
The Telemedicine unit mainly consists of four modules, the biosignal acquisition module, which is responsible for biosignals acquisition, a digital camera responsible for image capturing, a processing unit, which is basically a Personal Computer, and a communication module (GSM, Satellite or POTS modem).
The biosignal acquisition module was designed to operate with some of the most common portable biosignal monitors used in emergency cases or in Intensive care Units such as a) CRITIKON DINAMAP PLUS Monitor Model 8700/9700 family of monitors, b)
PROTOCOL-Welch Allyn Propaq 1xx Vital Signs Monitor, c) PROTOCOL-Welch Allyn Propaq Encore 2xx Vital Signs Monitor.
The biosignals collected by the patient (and then transmitted to the Base Unit) are:
• ECG up to 12 lead, depending on the monitor used in each case.
• Oxygen Saturation (SpO2).
• Heart Rate (HR).
• Non-Invasive Blood Pressure (NIBP).
• Invasive blood Pressure (IP).
• Temperature (Temp)
• Respiration (Resp)
The PC used depends on the type of the Telemedicine application (role of the Telemedicine unit). As shown in Table 1: a) in cases where the autonomy and small size of the system are important (mainly in ambulances), a sub notebook like Toshiba libretto 100 ct portable PC is used, a picture of a portable device is shown in Figure 3 b) in cases where we need some autonomy but size is not considered an important element a Typical Pentium portable PC is used; c) in cases where we do not necessarily need autonomy, portability and small system size, a Typical Pentium Desktop PC is used.
The control of the Telemedicine unit is fully automatic. The only thing the telemedicine unit user has to do is connect the biosignal monitor to the patient and turn on the PC. The PC then performs the connection to the base unit automatically. Although the base unit basically controls the overall system operation, the Telemedicine unit user can also execute a number of commands. This option is useful when the system is used in a distance health center or in a ship and a conversation between the two sites takes place.
b) Base Unit (or Doctor's Unit)
The base unit mainly consists of a dedicated PC equipped with a modem, which is responsible for data interchange. In addition the base unit pc is responsible for displaying incoming signals from the Telemedicine unit. When an expert doctor uses the base unit located outside the hospital area (like in the Intensive Care Room application – see Figure 1, a portable PC equipped with a GSM modem or a desktop PC equipped with a POTS modem is used. When the base unit is located in the hospital, a desktop PC connected to the Hospital Information Network (HIS) equipped with a POTS modem can additionally be used; the expert doctor uses it as a processing terminal.
Through the base unit, user has the full control of the telemedicine session. The user is able to monitor the connection with a client (telemedicine unit), send commands to the telemedicine unit such as the operation mode (biosignals or images) Figure 4. In cases were the base station is connected to a Hospital LAN the user can choose to which of the
telemedicine units to connect to, as shown in Figure 5 the user of the base unit is able to choose and connect to anyone of the telemedicine units connected on the network. The units connected on the network can be ICU telemedicine units or distance mobile telemedicine units connected through phone lines.
The Base Unit's user can monitor biosignals or still images coming from the Telemedicine unit, thus keeping a continuous online communication with the patient site. This unit has the full control of the Telemedicine session. The doctor (user) can send all possible commands concerning both still image transmission and biosignals transmission. Figure 6 presents a typical biosignal-receiving window (continuous operation).
c) Technical Constraints – Feasibility Biosignals transmission
Along with biosignals, information concerning the monitor, such as the alarms or the monitor status, is transmitted from the Telemedicine unit to the base unit. The ECG waveform and SpO2 or Co2 Waveform (where available) is the continuous signals transmitted, trends are transmitted for the rest of data. ECG data are sampled at a rate of 200 samples/sec by 10 bits/sample or 12 bits/sample, for all monitors used, thus resulting in a generation of 2000 bits/sec and 2400 bits/sec for one ECG channel. SpO2 and Co2 waveforms are sampled at a rate of 100 samples/sec by 10 bit/sample; thus resulting in a generation of 1000 bits/sec for one channel. Trends for SpO2, HR, NIBP, BP, Temp and monitor data are updated with a refresh rate of one per second, thus adding a small fraction of data to be transmitted approximately up to 200 bits/sec. All biosignals monitors used with the system can provide digital output of the collected signals [36-38].
Image transmission
Images captured by the Telemedicine unit's camera have resolution 320 × 240 pixel and are compressed using the JPEG compression algorithm; the resulting data set is approximately 5–6 KB depending on the compression rate used for the JPEG algorithm [39].
Transmission rate
The signals transmission is done using GSM, Satellite and POTS links. For the time being, the GSM network that the system was technically tested on; allows transmission of data up to 9600 bps (when operating on the normal mode) and is able to reach up to 43200 bps when using the HSDC (High Speed Circuit Switched Data). The satellite links transmission rate depends on the equipment and the satellite system used in each case; it has a range from 2400 bps up to 64000 bps. The use of different satellite systems can increase the cost of equipment and cost of use; in our case we had used an
INMARSAT-phone Mini-m system which can transmit data only up to 2400 bps, but has low equipment and use cost. Plain Old Telephony System (POTS) allows the transmission of data using a rate up to 56000 bps, thus enabling the continuous and fast information transmission (Table 2).
The practical maximum data transfer rate over telecommunication means is never as high as the theoretical data transfer rate. Practical data rates depend on the time and the area where the system is used. Biosignals data transmission can be done in two ways: real time transmission where a continuous signal is transmitted from client to server or store and forward transmission where signals of a predefined period of time are stored in the client and transmitted as files to server. It mainly depends on the maximum data transfer rate of the telecommunication link used and the digital data output that the biosignal monitor has in each case.
Results – Discussion
The final result is a "Multi-purpose" Telemedicine system, which facilitates a flexible architecture that can be adopted in several different application fields. The system has been tested and validated for a variety of medical devices and telecommunication means. Results presented in this section are typical for the needs of system use in Rural Health Centers, in Ambulance Vehicles or in a Navigating Ship.
Data transmission is done using the TCP/IP network protocol. Transmitting data over TCP/IP is a trivial and easy task when using networks, which have high bandwidth and low error rate. In order to transmit a buffer of n bytes through TCP/IP a header of about 55 bytes is added, this will add a great amount of data especially in cases that we transmit small buffers (e.g. when transmitting a buffer of 10 bytes the network protocol will increase this buffer to 65 bytes). When transmitting a buffer that has size larger than the Maximum Transfer Unit (MTU) this buffer will be fragmented in to smaller packets that each one has the size of the MTU, all small packets will be reconnected when arriving at the destination site; this case will cause problems when one of the fragmentation packets is lost [42]。