cdma

现代移动通信，究竟是如何崛起的？

由 自作多情 提交于 2020-02-15 08:03:52
▋Part.1： 电报电话，近现代通信的开篇 通信的历史，从人类文明诞生的那一天就开始了。 在原始社会，部落成员进行狩猎活动时，就会互相通信。不过当时的通信方式较为落后，“基本靠吼”。 随着历史车轮缓缓向前，人类社会组织规模不断扩大，出现了城邦甚至国家。通信技术也随之不断演进，引入了很多新颖的通信方式和工具。例如大家耳熟能详的烽火旗语、击鼓鸣金、驿站书信等等。 这些通信手段虽然落后，但是加强了社会组织之间的联系，也促进了人与人之间的情感交流，极大地推动了人类文明的进步。 到了19世纪，随着电磁理论的出现和成熟，通信技术终于迎来了跨越式的发展。 1837年，美国人塞缪尔·莫尔斯（Samuel Morse）发明了莫尔斯电码和有线电报。莫尔斯的发明具有划时代的意义——它让人类获得了一种全新的信息传递方式，这种方式“看不见”、“摸不着”、“听不到”，完全不同于以往。 塞缪尔·莫尔斯（1791-1872） 1839年，全球首条真正投入运营的电报线路在英国出现。这条线路长约20公里，由查尔斯·惠世通和威廉·库克发明。 39年后的1876年，美国人亚历山大·贝尔（Alexander Bell）申请了电话专利，成为了电话之父。虽然真正的电话之父应该是安东尼奥·穆齐（Antonio Meucci），但他当时一贫如洗，连申请专利的钱都没有，导致被贝尔捡漏。 亚历山大·贝尔（1847-1922）

CDMA PDU parsing on Android

由 巧了我就是萌 提交于 2020-02-01 07:59:12
问题 I have written a program to decode a CDMA 3GPP2 point-to-point SMS message. I tested it on a couple CDMA PDU hex strings I found on the internet, and it works perfectly. However, when I try to implement it on all incoming text messages on the Android platform, it always fails. I took a look at the incoming PDU, and it doesn't seem to follow the same pattern I have been used to seeing. Can anyone explain what format this PDU is in, or what I am missing to correctly decode this PDU? Is there

How to check iPhone network type GSM or CDMA

由 牧云@^-^@ 提交于 2020-01-11 08:41:12
问题 In my application I need to check network type GSM or CDMA (for Verizon). I found CTCarrier class which contains property mobileNetworkCode, but I don't wanna hardcode value for each providers. Are there other ways to check it? Please help. 回答1: You could get that through the Model#, but then again, you have to hardcode a list of Model# and compare them. 回答2: Maybe you could do that by checking the IP Address of the iPhone if it is wireless connected. If once detected it would´t change unless

无线相关术语

由 半世苍凉 提交于 2020-01-10 10:42:56
802.11 802.11是IEEE最初制定的一个无线局域网标准，主要用于解决办公室局域网和校园网中用户与用户终端的无线接入，业务主要限于数据存取，速率最高只能达到2Mbps。由于它在速率和传输距离上都不能满足人们的需要，因此，IEEE小组又相继推出了802.11b和802.11a两个新标准，前者已经成为目前的主流标准，而后者也被很多厂商看好。 802.11b 802.11b采用2.4GHz直接序列扩频，最大数据传输速率为11Mb/s，无须直线传播。动态速率转换当射频情况变差时，可将数据传输速率降低为5.5Mb/s、2Mb/s和1Mb/s。使用范围 支持的范围是在室外为300米，在办公环境中最长为100米。802.11b使用与以太网类似的连接协议和数据包确认，来提供可靠的数据传送和网络带宽的有效使用。 802.11a 802.11a标准是已在办公室、家庭、宾馆、机场等众多场合得到广泛应用的802.11b无线联网标准的后续标准。它工作在5GHzU-NII频带，物理层速率可达54Mb/s，传输层可达25Mbps。可提供25Mbps的无线ATM接口和10Mbps的以太网无线帧结构接口，以及TDD/TDMA的空中接口；支持语音、数据、图像业务；一个扇区可接入多个用户，每个用户可带多个用户终端。 现在一些厂商对于该标准的计划已提到议事日程。例如

有中国特色的紧急呼叫

由 |▌冷眼眸甩不掉的悲伤 提交于 2020-01-01 09:51:42
一篇老文，炒回冷饭 ：） "您好，匪警请拨110，火警请拨119，急救中心请拨120，交通故障请拨122" 。相信很多人在国内手机拨打紧急呼叫号码时都会听到这个熟悉的语音台自动播放。前几年315晚会上也有消费者投诉过国内无卡情况下，甚至用户欠费下，手机拨打紧急呼叫就是个摆设，大家百度下也会发现诸如下类新闻： 原因就在于中国移动和中国联通：只有在SIM卡激活并且获得正常服务（不欠费）的情况下， 紧急呼叫号码(110, 119, 120, 122, 999) 才会被紧急呼叫服务中心处理， 且要求紧急呼叫按照正常呼叫信令流程拨出，否则其余情况（包括无卡，包括拨打国际通用紧急号码911，112）均是按照紧急呼叫信令流程拨出。而对于中国电信：由于CDMA下不分紧急呼叫或者正常呼叫，紧急呼叫号码由网络侧判别是否是紧急呼叫，均会被紧急呼叫服务中心处理。 如果按照紧急呼叫流程拨出后，电话始终在振铃阶段，播放那段经典的回铃音： 总结起来，见下表： 还记得HardCoded类型的ECC么？如果忘记了，请查阅上一期《 紧急呼叫这点事儿 (一) 》。Q平台把中国特色的110、119、120、122、999放到了 NV#69737 /nv/item_files/pbm/pbm_hardcoded_ecc_list ，见下图 这里绿色椭圆框框中的emergency_mode = 0x02 任何制式均可发起

Why getBaseStationLatitude() keeps returning the Integer.MAX_VALUE (unknown)?

由 ╄→гoц情女王★ 提交于 2019-12-24 09:58:04
问题 Class project & thesis work - trying to pull information from CDMA Cell, specifically by using the getBaseStationLatitude() & getBaseStationLongitude(). The value being returned is the MAX_VALUE (2147483647) - I'm not receiving actual lat/longs. getBaseStationID(), getNetworkID() & getSystemID() are returning valid id's. I've tested this in 2 separate cells with no luck. My code is posted below. Both ACCESS_FINE_LOCATION & ACCESS_COURSE_LOCATION are added to manifest. Testing done on Droid,

Is telephony manager values reliable and changeable (cdma)?

由 Deadly 提交于 2019-12-23 17:21:46
问题 I want to know if I can rely on the telephony values like country, MCC, etc on Android for my app. Can I change them on the run using setprop? I tried changing using setprop it didn't seem to work. From my understanding telephony manager is a class/interface which represents Hardware configuration of GSM or CDMA. In case of GSM this could be sim and in case of CDMA it cud be a hardware. My questions are: Who update these values in both the cases for the first time? Are these values are saved

Android GSM/CDMA cell reload

由 六眼飞鱼酱① 提交于 2019-12-12 05:06:34
问题 I have problem (challenge) with my app. I want to be connected to the "best" GSM or CDMA cell - the closest, with the best signal, etc... As I turned off the cell-phone functions and turned it on back. That is the thing I want to do in my app, because I need to have the most recent informations of location without using GPS or any data. Can I find the way, how to force Android to refind the GSM/CDMA cell? Lot of thanks for all! 回答1: For GSM, the cell you are connected to is decided by the

Cellular AT Command sets. How universal are they

由 ♀尐吖头ヾ 提交于 2019-12-11 20:13:29
问题 Pretty much every phone that has bluetooth (so pretty much every phone) has an AT command interface for controlling the phone. Some base commands are universal due to the fact theat they precede the cellular phones (ATDT, ATA, ATZ, etc). But there are many AT commands implmented specifcally to control or query cellular connection specific data. Are these commands at least somewhat standardized? If so, how? UMTS vs EVDO, Manufacture, etc.. 回答1: There is a 3GPP standard for AT commands: http:/

signalStrength.getGsmSignalStrength() is giving values without sim-card also

由 三世轮回 提交于 2019-12-11 17:47:56
问题 Hey I tried for signalStrength.getGsmSignalStrength() for GSM and CDMA devices but I noticed that both the devices gives strength even when sim is not inserted in device.I want to place a call or send message only if network is good how can I achieve this? And also want to know which signal strength this API returns!!... Please reply as soon as possible. public class AndroidPhoneStateListener extends PhoneStateListener { public static int signalStrengthValue; @Override public void
订阅 cdma