2010年7月16日 星期五
2010年1月6日 星期三
人肉搜尋真可怕 該如何避免？
台大批踢踢（TELNET://PTT.CC）上的事件，又一次轉變為社會新聞，而一般人，則再一次感受到網路的可怕。專家們總是說，這是一種「網路暴力」、是一種「網路霸凌」；實際上在這許多次的網路「人肉搜尋」事件當中，並沒有哪一次，網友們是透過非法手段取得隱私資料來進行公佈，這一切的資料，都大大方方的流通在網路上，任人取用。
【人肉搜尋】
人肉搜尋是個大陸名詞，在批踢踢通常稱為「查IP」，泛指透過大量的網友進行搜尋，由於網友人數眾多，能夠從網路上搜尋、過濾、篩選出來的資料也十分龐大，並能夠發揮合作力量共同校正找出正確的資訊。
【資料來源】
有哪些地方容易洩漏你的個人資料呢？通常可以歸納為以下幾種來源，仔細看一看你可以知道，這一切的資料，真的都是公開在網路上的資料，並沒有什麼是所謂的「隱私」資料：
一、在網誌中使用真名
二、在相簿中使用真名
三、各級學校考試榜單
四、各種學校公告事項
五、政府機關公告事項
六、社團或班級版面資訊
七、自己在網路上描述個人背景與事蹟
【人肉搜尋流程】
一、首先透過網友的帳號（id）在搜尋引擎（如Google）進行搜尋，通常可以由此找到或確認其在網路上的慣用帳號或暱稱，若有網誌、相簿也會在此步驟中呈現出來。
二、開始分析網友的網誌、相簿、MSN帳號、即時通帳號以及有註冊帳號過的網站，檢查與事件有關的蛛絲馬跡。
三、若有網誌或相簿，且放在社群網站上（如無名、痞客邦、facebook）時，由於社群網站有好友關係能夠進行分析，且使用者通常會對好友下暱稱，此時透過「雙向好友」關係即可確認該網友的周遭朋友。
四、取得好友相對關係後，即可開始分析在好友眼中的網友，此時可順便收集網友更詳細的資料。
五、進行資料整理，並與網友得到的訊息比對。
六、人肉搜尋大功告成。
【誰該負責】
是誰透漏了這些資料？為什麼我的資料會在網路上流傳？為什麼網友那麼容易找到我的朋友、家人、同學？誰該替我負責？實際上，就是你自己、你的朋友、家人、同學，應該替你負責。若你沒有留下與朋友交往的蛛絲馬跡，若朋友沒有在照片中提到你的名字、若家人的網誌相簿沒有與你做出相互連結，那麼網友要搜尋到你，難上加難。【自我防範】要如何防範別人對我人肉搜尋？說真的行得正坐得直，一般網友也沒有辦法對你人肉搜尋。要知道，人肉搜尋需要的就是「人」，若你沒有犯下眾怒，實際上並不會有人能夠「動員」起那麼多的網友來針對你進行搜尋。另一方面，自己在網路上公佈資訊時，也要適當的做好防範，不要以為自己是把資料張貼在社團版面或是班級版面，就可以把所有的資料都寫出來。要記得，網路是無遠弗屆的，今天你一旦寫在網路上，這些資料甚至可能保留在搜尋引擎當中超過十年。因此，在公開的地方（沒有進行權限控管的網站、討論區），就要好好的保護自己的隱私。
不宜在網路上張貼的個人資料：
一、本名（雖然仍有可能被其他人洩漏，但最起碼自己要做好）
二、家中詳細地址（只應寫到區域，如永和）
三、即時通訊帳號（先進行一般交流，熟稔後再私下給MSN帳號、即時通帳號）
四、不必要時，不需寫到目前學校或公司
五、電話（一般人肉搜尋時，很少用到電話，但為了隱私起見仍建議不張貼）
【人肉搜尋】
人肉搜尋是個大陸名詞，在批踢踢通常稱為「查IP」，泛指透過大量的網友進行搜尋，由於網友人數眾多，能夠從網路上搜尋、過濾、篩選出來的資料也十分龐大，並能夠發揮合作力量共同校正找出正確的資訊。
【資料來源】
有哪些地方容易洩漏你的個人資料呢？通常可以歸納為以下幾種來源，仔細看一看你可以知道，這一切的資料，真的都是公開在網路上的資料，並沒有什麼是所謂的「隱私」資料：
一、在網誌中使用真名
二、在相簿中使用真名
三、各級學校考試榜單
四、各種學校公告事項
五、政府機關公告事項
六、社團或班級版面資訊
七、自己在網路上描述個人背景與事蹟
【人肉搜尋流程】
一、首先透過網友的帳號（id）在搜尋引擎（如Google）進行搜尋，通常可以由此找到或確認其在網路上的慣用帳號或暱稱，若有網誌、相簿也會在此步驟中呈現出來。
二、開始分析網友的網誌、相簿、MSN帳號、即時通帳號以及有註冊帳號過的網站，檢查與事件有關的蛛絲馬跡。
三、若有網誌或相簿，且放在社群網站上（如無名、痞客邦、facebook）時，由於社群網站有好友關係能夠進行分析，且使用者通常會對好友下暱稱，此時透過「雙向好友」關係即可確認該網友的周遭朋友。
四、取得好友相對關係後，即可開始分析在好友眼中的網友，此時可順便收集網友更詳細的資料。
五、進行資料整理，並與網友得到的訊息比對。
六、人肉搜尋大功告成。
【誰該負責】
是誰透漏了這些資料？為什麼我的資料會在網路上流傳？為什麼網友那麼容易找到我的朋友、家人、同學？誰該替我負責？實際上，就是你自己、你的朋友、家人、同學，應該替你負責。若你沒有留下與朋友交往的蛛絲馬跡，若朋友沒有在照片中提到你的名字、若家人的網誌相簿沒有與你做出相互連結，那麼網友要搜尋到你，難上加難。【自我防範】要如何防範別人對我人肉搜尋？說真的行得正坐得直，一般網友也沒有辦法對你人肉搜尋。要知道，人肉搜尋需要的就是「人」，若你沒有犯下眾怒，實際上並不會有人能夠「動員」起那麼多的網友來針對你進行搜尋。另一方面，自己在網路上公佈資訊時，也要適當的做好防範，不要以為自己是把資料張貼在社團版面或是班級版面，就可以把所有的資料都寫出來。要記得，網路是無遠弗屆的，今天你一旦寫在網路上，這些資料甚至可能保留在搜尋引擎當中超過十年。因此，在公開的地方（沒有進行權限控管的網站、討論區），就要好好的保護自己的隱私。
不宜在網路上張貼的個人資料：
一、本名（雖然仍有可能被其他人洩漏，但最起碼自己要做好）
二、家中詳細地址（只應寫到區域，如永和）
三、即時通訊帳號（先進行一般交流，熟稔後再私下給MSN帳號、即時通帳號）
四、不必要時，不需寫到目前學校或公司
五、電話（一般人肉搜尋時，很少用到電話，但為了隱私起見仍建議不張貼）
2009年11月24日 星期二
What is GPRS!!
General packet radio service (GPRS) is a packet oriented mobile data service available to users of the 2G cellular communication systems global system for mobile communications (GSM), as well as in the 3G systems. In 2G systems, GPRS provides data rates of 56-114 kbit/s.
GPRS data transfer is typically charged per megabyte of traffic transferred, while data communication via traditional circuit switching is billed per minute of connection time, independent of whether the user actually is using the capacity or is in an idle state. GPRS is a best-effort packet switched service, as opposed to circuit switching, where a certain quality of service (QoS) is guaranteed during the connection for non-mobile users.
2G cellular systems combined with GPRS are often described as 2.5G, that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate speed data transfer, by using unused time division multiple access (TDMA) channels in, for example, the GSM system. Originally there was some thought to extend GPRS to cover other standards, but instead those networks are being converted to use the GSM standard, so that GSM is the only kind of network where GPRS is in use. GPRS is integrated into GSM Release 97 and newer releases. It was originally standardized by European Telecommunications Standards Institute (ETSI), but now by the 3rd Generation Partnership Project (3GPP).
GPRS was developed as a GSM response to the earlier CDPD and i-mode packet switched cellular technologies.
[edit] Technical overview
[edit] Services offered
GPRS extends the GSM circuit switched data capabilities and makes the following services possible:
"Always on" internet access
Multimedia messaging service (MMS)
Push to talk over cellular (PoC/PTT)
Instant messaging and presence—wireless village
Internet applications for smart devices through wireless application protocol (WAP)
Point-to-point (P2P) service: inter-networking with the Internet (IP)
If SMS over GPRS is used, an SMS transmission speed of about 30 SMS messages per minute may be achieved. This is much faster than using the ordinary SMS over GSM, whose SMS transmission speed is about 6 to 10 SMS messages per minute
[edit] Protocols supported
GPRS supports the following protocols:
internet protocol (IP). In practice, the mobile built-in browser uses IPv4 since IPv6 is not yet popular.
point-to-point protocol (PPP). In this mode PPP is often not supported by the mobile phone operator but if the mobile is used as a modem to the connected computer, PPP is used to tunnel IP to the phone. This allows an IP address to be assigned dynamically to the mobile equipment.
X.25 connections. This is typically used for applications like wireless payment terminals, although it has been removed from the standard. X.25 can still be supported over PPP, or even over IP, but doing this requires either a network based router to perform encapsulation or intelligence built in to the end-device/terminal; e.g., user equipment (UE).
When TCP/IP is used, each phone can have one or more IP addresses allocated. GPRS will store and forward the IP packets to the phone during cell handover (when you move from one cell to another). TCP handles any packet loss (e.g. due to a radio noise induced pause) resulting in a temporary throttling in transmission speed.
[edit] Hardware
Devices supporting GPRS are divided into three classes:
Class A
Can be connected to GPRS service and GSM service (voice, SMS), using both at the same time. Such devices are known to be available today.
Class B
Can be connected to GPRS service and GSM service (voice, SMS), but using only one or the other at a given time. During GSM service (voice call or SMS), GPRS service is suspended, and then resumed automatically after the GSM service (voice call or SMS) has concluded. Most GPRS mobile devices are Class B.
Class C
Are connected to either GPRS service or GSM service (voice, SMS). Must be switched manually between one or the other service.
A true Class A device may be required to transmit on two different frequencies at the same time, and thus will need two radios. To get around this expensive requirement, a GPRS mobile may implement the dual transfer mode (DTM) feature. A DTM-capable mobile may use simultaneous voice and packet data, with the network coordinating to ensure that it is not required to transmit on two different frequencies at the same time. Such mobiles are considered pseudo-Class A, sometimes referred to as "simple class A". Some networks are expected to support DTM in 2007.
Huawei E220 Modem
USB GPRS modems use a terminal-like interface USB 2.0 and later, data formats V.42bis, and RFC 1144 and external antennas. Modems can be added as cards (for laptops) or external USB devices which are similar in shape and size to a computer mouse.
[edit] Coding schemes and speeds
The upload and download speeds that can be achieved in GPRS depend on a number of factors such as:
the number of BTS TDMA time slots assigned by the operator
the maximum capability of the mobile device expressed as a GPRS multislot class
the channel encoding used summarised in the following table.
The least robust, but fastest, coding scheme (CS-4) is available near a base transceiver station (BTS), while the most robust coding scheme (CS-1) is used when the mobile station (MS) is further away from a BTS.
Using the CS-4 it is possible to achieve a user speed of 20.0 kbit/s per time slot. However, using this scheme the cell coverage is 25% of normal. CS-1 can achieve a user speed of only 8.0 kbit/s per time slot, but has 98% of normal coverage. Newer network equipment can adapt the transfer speed automatically depending on the mobile location.
In addition to GPRS, there are two other GSM technologies which deliver data services: circuit-switched data (CSD) and high-speed circuit-switched data (HSCSD). In contrast to the shared nature of GPRS, these instead establish a dedicated circuit (usually billed per minute). Some applications such as video calling may prefer HSCSD, especially when there is a continuous flow of data between the endpoints.
The following table summarises some possible configurations of GPRS and circuit switched data services.
[edit] Multiple access schemes
The multiple access methods used in GSM with GPRS are based on frequency division duplex (FDD) and TDMA. During a session, a user is assigned to one pair of up-link and down-link frequency channels. This is combined with time domain statistical multiplexing; i.e., packet mode communication, which makes it possible for several users to share the same frequency channel. The packets have constant length, corresponding to a GSM time slot. The down-link uses first-come first-served packet scheduling, while the up-link uses a scheme very similar to reservation ALOHA (R-ALOHA). This means that slotted ALOHA (S-ALOHA) is used for reservation inquiries during a contention phase, and then the actual data is transferred using dynamic TDMA with first-come first-served scheduling.
[edit] Addressing
A GPRS connection is established by reference to its access point name (APN). The APN defines the services such as wireless application protocol (WAP) access, short message service (SMS), multimedia messaging service (MMS), and for Internet communication services such as email and World Wide Web access.
In order to set up a GPRS connection for a wireless modem, a user must specify an APN, optionally a user name and password, and very rarely an IP address, all provided by the network operator
[edit] Usability
The maximum speed of a GPRS connection offered in 2003 was similar to a modem connection in an analog wire telephone network, about 32-40 kbit/s, depending on the phone used. Latency is very high; round-trip time (RTT) is typically about 600-700 ms and often reaches 1 s. GPRS is typically prioritized lower than speech, and thus the quality of connection varies greatly.
Devices with latency/RTT improvements (via, for example, the extended UL TBF mode feature) are generally available. Also, network upgrades of features are available with certain operators. With these enhancements the active round-trip time can be reduced, resulting in significant increase in application-level throughput speeds.
GPRS data transfer is typically charged per megabyte of traffic transferred, while data communication via traditional circuit switching is billed per minute of connection time, independent of whether the user actually is using the capacity or is in an idle state. GPRS is a best-effort packet switched service, as opposed to circuit switching, where a certain quality of service (QoS) is guaranteed during the connection for non-mobile users.
2G cellular systems combined with GPRS are often described as 2.5G, that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate speed data transfer, by using unused time division multiple access (TDMA) channels in, for example, the GSM system. Originally there was some thought to extend GPRS to cover other standards, but instead those networks are being converted to use the GSM standard, so that GSM is the only kind of network where GPRS is in use. GPRS is integrated into GSM Release 97 and newer releases. It was originally standardized by European Telecommunications Standards Institute (ETSI), but now by the 3rd Generation Partnership Project (3GPP).
GPRS was developed as a GSM response to the earlier CDPD and i-mode packet switched cellular technologies.
[edit] Technical overview
[edit] Services offered
GPRS extends the GSM circuit switched data capabilities and makes the following services possible:
"Always on" internet access
Multimedia messaging service (MMS)
Push to talk over cellular (PoC/PTT)
Instant messaging and presence—wireless village
Internet applications for smart devices through wireless application protocol (WAP)
Point-to-point (P2P) service: inter-networking with the Internet (IP)
If SMS over GPRS is used, an SMS transmission speed of about 30 SMS messages per minute may be achieved. This is much faster than using the ordinary SMS over GSM, whose SMS transmission speed is about 6 to 10 SMS messages per minute
[edit] Protocols supported
GPRS supports the following protocols:
internet protocol (IP). In practice, the mobile built-in browser uses IPv4 since IPv6 is not yet popular.
point-to-point protocol (PPP). In this mode PPP is often not supported by the mobile phone operator but if the mobile is used as a modem to the connected computer, PPP is used to tunnel IP to the phone. This allows an IP address to be assigned dynamically to the mobile equipment.
X.25 connections. This is typically used for applications like wireless payment terminals, although it has been removed from the standard. X.25 can still be supported over PPP, or even over IP, but doing this requires either a network based router to perform encapsulation or intelligence built in to the end-device/terminal; e.g., user equipment (UE).
When TCP/IP is used, each phone can have one or more IP addresses allocated. GPRS will store and forward the IP packets to the phone during cell handover (when you move from one cell to another). TCP handles any packet loss (e.g. due to a radio noise induced pause) resulting in a temporary throttling in transmission speed.
[edit] Hardware
Devices supporting GPRS are divided into three classes:
Class A
Can be connected to GPRS service and GSM service (voice, SMS), using both at the same time. Such devices are known to be available today.
Class B
Can be connected to GPRS service and GSM service (voice, SMS), but using only one or the other at a given time. During GSM service (voice call or SMS), GPRS service is suspended, and then resumed automatically after the GSM service (voice call or SMS) has concluded. Most GPRS mobile devices are Class B.
Class C
Are connected to either GPRS service or GSM service (voice, SMS). Must be switched manually between one or the other service.
A true Class A device may be required to transmit on two different frequencies at the same time, and thus will need two radios. To get around this expensive requirement, a GPRS mobile may implement the dual transfer mode (DTM) feature. A DTM-capable mobile may use simultaneous voice and packet data, with the network coordinating to ensure that it is not required to transmit on two different frequencies at the same time. Such mobiles are considered pseudo-Class A, sometimes referred to as "simple class A". Some networks are expected to support DTM in 2007.
.jpg){kind=link}
Huawei E220 Modem
USB GPRS modems use a terminal-like interface USB 2.0 and later, data formats V.42bis, and RFC 1144 and external antennas. Modems can be added as cards (for laptops) or external USB devices which are similar in shape and size to a computer mouse.
[edit] Coding schemes and speeds
The upload and download speeds that can be achieved in GPRS depend on a number of factors such as:
the number of BTS TDMA time slots assigned by the operator
the maximum capability of the mobile device expressed as a GPRS multislot class
the channel encoding used summarised in the following table.
The least robust, but fastest, coding scheme (CS-4) is available near a base transceiver station (BTS), while the most robust coding scheme (CS-1) is used when the mobile station (MS) is further away from a BTS.
Using the CS-4 it is possible to achieve a user speed of 20.0 kbit/s per time slot. However, using this scheme the cell coverage is 25% of normal. CS-1 can achieve a user speed of only 8.0 kbit/s per time slot, but has 98% of normal coverage. Newer network equipment can adapt the transfer speed automatically depending on the mobile location.
In addition to GPRS, there are two other GSM technologies which deliver data services: circuit-switched data (CSD) and high-speed circuit-switched data (HSCSD). In contrast to the shared nature of GPRS, these instead establish a dedicated circuit (usually billed per minute). Some applications such as video calling may prefer HSCSD, especially when there is a continuous flow of data between the endpoints.
The following table summarises some possible configurations of GPRS and circuit switched data services.
[edit] Multiple access schemes
The multiple access methods used in GSM with GPRS are based on frequency division duplex (FDD) and TDMA. During a session, a user is assigned to one pair of up-link and down-link frequency channels. This is combined with time domain statistical multiplexing; i.e., packet mode communication, which makes it possible for several users to share the same frequency channel. The packets have constant length, corresponding to a GSM time slot. The down-link uses first-come first-served packet scheduling, while the up-link uses a scheme very similar to reservation ALOHA (R-ALOHA). This means that slotted ALOHA (S-ALOHA) is used for reservation inquiries during a contention phase, and then the actual data is transferred using dynamic TDMA with first-come first-served scheduling.
[edit] Addressing
A GPRS connection is established by reference to its access point name (APN). The APN defines the services such as wireless application protocol (WAP) access, short message service (SMS), multimedia messaging service (MMS), and for Internet communication services such as email and World Wide Web access.
In order to set up a GPRS connection for a wireless modem, a user must specify an APN, optionally a user name and password, and very rarely an IP address, all provided by the network operator
[edit] Usability
The maximum speed of a GPRS connection offered in 2003 was similar to a modem connection in an analog wire telephone network, about 32-40 kbit/s, depending on the phone used. Latency is very high; round-trip time (RTT) is typically about 600-700 ms and often reaches 1 s. GPRS is typically prioritized lower than speech, and thus the quality of connection varies greatly.
Devices with latency/RTT improvements (via, for example, the extended UL TBF mode feature) are generally available. Also, network upgrades of features are available with certain operators. With these enhancements the active round-trip time can be reduced, resulting in significant increase in application-level throughput speeds.
2009年10月7日 星期三
3GPP Long Term Evolution ( LTE )
3GPP Long Term Evolution
From Wikipedia, the free encyclopedia
LTE (Long Term Evolution) is the last step toward the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile telephone networks. Where the current generation of mobile telecommunication networks are collectively known as 3G (for "third generation"), LTE is marketed as 4G. Most major mobile carriers in the United States and several worldwide carriers have announced plans to convert their networks to LTE beginning in 2009. LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) which will be introduced in 3rd Generation Partnership Project (3GPP) Release 8. Much of 3GPP Release 8 will focus on adopting 4G mobile communications technology, including an all-IP flat networking architecture. On August 18, 2009, the European Commission announced it will invest a total of €18 million into researching the deployment of LTE and LTE Advanced.[1]
While it is commonly seen as a mobile telephone or common carrier development, public safety agencies (and US Intelligence Services) in the US[2] have also endorsed LTE as the preferred technology for the new 700 MHz public-safety radio band. Agencies in some areas have filed for waivers[3] hoping to use the 700 MHz[4] spectrum with other technologies in advance of the adoption of a nationwide standard.
Contents[hide] |
[edit]Overview
The LTE specification provides downlink peak rates of at least 100 Mbps, an uplink of at least 50 Mbit/s and RAN round-trip times of less than 10 ms. LTE supports scalable carrierbandwidths, from 20 MHz down to 1.4 MHz and supports both Frequency Division Duplexing and Time Division Duplexing.
Part of the LTE standard is the System Architecture Evolution, a flat IP-based network architecture designed to replace the GPRS Core Network and ensure support for, and mobility between, some legacy or non-3GPP systems, for example GPRS and WiMax respectively.[5]
The main advantages with LTE are high throughput, low latency, plug and play, FDD and TDD in the same platform, improved end-user experience and simple architecture resulting in low operating costs. LTE will also support seamless passing to cell towers with older network technology such as GSM, cdmaOne, W-CDMA (UMTS), and CDMA2000.
[edit]Current state
While 3GPP Release 8 is an unratified, formative standard, much of the Release addresses upgrading 3G UMTS to 4G mobile communications technology, which is essentially a mobile broadband system with enhanced multimedia services built on top.
The standard includes:
- Peak download rates of 326.4 Mbit/s for 4x4 antennas, 172.8 Mbit/s for 2x2 antennas for every 20 MHz of spectrum.[6]
- Peak upload rates of 86.4 Mbit/s for every 20 MHz of spectrum.[6]
- 5 different terminal classes have been defined from a voice centric class up to a high end terminal that supports the peak data rates. All terminals will be able to process 20 MHz bandwidth.
- At least 200 active users in every 5 MHz cell. (specifically, 200 active data clients)
- Sub-5ms latency for small IP packets
- Increased spectrum flexibility, with spectrum slices as small as 1.5 MHz (and as large as 20 MHz) supported (W-CDMA requires 5 MHz slices, leading to some problems with roll-outs of the technology in countries where 5 MHz is a commonly allocated amount of spectrum, and is frequently already in use with legacy standards such as 2G GSM and cdmaOne.) Limiting sizes to 5 MHz also limited the amount of bandwidth per handset
- Optimal cell size of 5 km, 30 km sizes with reasonable performance, and up to 100 km cell sizes supported with acceptable performance
- Co-existence with legacy standards (users can transparently start a call or transfer of data in an area using an LTE standard, and, should coverage be unavailable, continue the operation without any action on their part using GSM/GPRS or W-CDMA-based UMTS or even 3GPP2 networks such as cdmaOne or CDMA2000)
- Support for MBSFN (Multicast Broadcast Single Frequency Network). This feature can deliver services such as Mobile TV using the LTE infrastructure, and is a competitor for DVB-H-based TV broadcast.
- PU2RC as a practical solution for MU-MIMO. The detailed procedure for the general MU-MIMO operation is handed to the next release, e.g., LTE-Advanced, where further discussions will be held.
A large amount of the work is aimed at simplifying the architecture of the system, as it transits from the existing UMTS circuit + packet switching combined network, to an all-IP flat architecture system.
[edit]Timetable
In December 2008, Rel-8 specification was locked. In January 2009, the ASN.1 code was locked. The standard has been complete enough that hardware designers have been designing chipsets, test equipment and base stations for some time. LTE test equipment has been shipping from several vendors since early 2008 and at the Mobile World Congress 2008 in Barcelona Ericsson demonstrated the world’s first end-to-end mobile call enabled by LTE on a small handheld device.[7] Motorola demonstrated a LTE RAN standard compliant eNodeB and LTE chipset at the same event.
[edit]An "All IP Network" (AIPN)
Next generation networks are based upon Internet Protocol (IP). See, for example, the Next Generation Mobile Networks Alliance (NGMN).[8]
In 2004, 3GPP proposed IP as the future for next generation networks and began feasibility studies into All IP Networks (AIPN). Proposals developed included recommendations for 3GPP Release 7(2005),[9] which are the foundation of higher level protocols such as LTE. These recommendations are part of the 3GPP System Architecture Evolution (SAE). Some aspects of All-IP networks, however, were already defined as early as release 4.[10]
[edit]E-UTRAN Air Interface
Release 8's air interface, E-UTRA (Evolved UTRAN, the E- prefix being common to the evolved equivalents of older UMTS components) would be used by UMTS operators deploying their own wireless networks. It's important to note that Release 8 is intended not just for use over E-UTRA, but is also indended for use over any other IP network, including WiMAX and WiFi, and even wired networks.[11]
The proposed E-UTRAN system uses OFDMA for the downlink (tower to handset) and Single Carrier FDMA (SC-FDMA) for the uplink and employs MIMO with up to four antennas per station. The channel coding scheme for transport blocks is turbo coding and a contention-free quadratic permutation polynomial (QPP) turbo code internal interleaver.[12]
The use of Orthogonal frequency-division multiplexing (OFDM), a system where the available spectrum is divided into many thin carriers, each on a different frequency, each carrying a part of the signal, enables E-UTRAN to be much more flexible in its use of spectrum than the older CDMA based systems that dominated 3G. CDMA networks require large blocks of spectrum to be allocated to each carrier, to maintain high chip rates, and thus maximize efficiency. Building radios capable of coping with different chip rates (and spectrum bandwidths) is more complex than creating radios that only send and receive one size of carrier, so generally CDMA based systems standardize both. Standardizing on a fixed spectrum slice has consequences for the operators deploying the system: too narrow a spectrum slice would mean the efficiency and maximum bandwidth per handset suffers; too wide a spectrum slice, and there are deployment issues for operators short on spectrum. This became a major issue with the US roll-out of UMTS over W-CDMA, where W-CDMA's 5 MHz requirement often left no room in some markets for operators to co-deploy it with existing GSM standards.
LTE supports both FDD and TDD mode. While FDD makes use of paired spectra for UL and DL transmission separated by a duplex frequency gap, TDD is alternating using the same spectral resources used for UL and DL, separated by guard time[13]. Each mode has its own frame structure within LTE and these are aligned with each other meaning that similar hardware can be used in the base stations and terminals to allow for economy of scale. The TDD mode in LTE is aligned with TD-SCDMA as well allowing for coexistence. Ericsson demonstrated at the MWC 2008 in Barcelona for the first time in the world both LTE FDD and TDD mode on the same base station platform.
[edit]Downlink
LTE uses OFDM for the downlink – that is, from the base station to the terminal. OFDM meets the LTE requirement for spectrum flexibility and enables cost-efficient solutions for very wide carriers with high peak rates. It is a well-established technology, for example in standards such as IEEE 802.11a/g, 802.16, HIPERLAN-2, DVB and DAB.
In the time domain there is a radio frame that is 10 ms long and consists of 10 sub frames of 1 ms each. Every sub frame consists of 2 slots where each slot is 0.5 ms. The subcarrier spacing in the frequency domain is 15 kHz. Twelve of these subcarriers together (per slot) is called a resource block so one resource block is 180 kHz. 6 Resource blocks fit in a carrier of 1.4 MHz and 100 resource blocks fit in a carrier of 20 MHz.
In the downlink there are three different physical channels. The Physical Downlink Shared Channel (PDSCH) is used for all the data transmission, the Physical Multicast Channel (PMCH) is used for broadcast transmission using a Single Frequency Network, and the Physical Broadcast Channel (PBCH) is used to send most important system information within the cell[14]. Supported modulation formats on the PDSCH are QPSK, 16QAM and 64QAM.
For MIMO operation, a distinction is made between single user MIMO, for enhancing one user's data throughput, and multi user MIMO for enhancing the cell throughput.
[edit]Uplink
In the uplink, LTE uses a pre-coded version of OFDM called Single Carrier Frequency Division Multiple Access (SC-FDMA). This is to compensate for a drawback with normal OFDM, which has a very high peak-to-average power ratio (PAPR). High PAPR requires expensive and inefficient power amplifiers with high requirements on linearity, which increases the cost of the terminal and drains the battery faster. SC-FDMA solves this problem by grouping together the resource blocks in a way that reduces the need for linearity, and so power consumption, in the power amplifier. A low PAPR also improves coverage and the cell-edge performance.
In the uplink there are two physical channels. While the Physical Random Access Channel (PRACH) is only used for initial access and when the UE is not uplink synchronized[15], all the data is being send on the Physical Uplink Shared Channel (PUSCH). Supported modulation formats on the uplink data channel are QPSK, 16QAM and 64QAM.
If virtual MIMO / Spatial division multiple access (SDMA) is introduced the data rate in the uplink direction can be increased depending on the number of antennas at the base station. With this technology more than one mobile can reuse the same resources.[16] l
[edit]Frequency bands and channel bandwidths
From Tables 5.5-1 "E-UTRA Operating Bands" and 5.6.1-1 "E-UTRA Channel Bandwidth" of 3GPP TS 36.101 (Release 8.4.0),[17] the following table lists the specified frequency bands of LTE and the channel bandwidths each listed band supports:
| [hide]E-UTRA Operating Band  | Uplink (UL) Operating Band BS Receive UE Transmit | Downlink (DL) Operating Band BS Transmit UE Receive | Duplex Mode | Channel Bandwidths (MHz) | Alias | Region(s) |
|---|---|---|---|---|---|---|
| I (1) | 1920 MHz to 1980 MHz | 2110 MHz to 2170 MHz | FDD | 5, 10, 15, 20 | UMTS IMT, "2100" | Japan, Europe, Asia |
| II (2) | 1850 MHz to 1910 MHz | 1930 MHz to 1990 MHz | FDD | 1.4, 3, 5, 10, 15, 20 | PCS, "1900" | United States, Latin America |
| III (3) | 1710 MHz to 1785 MHz | 1805 MHz to 1880 MHz | FDD | 1.4, 3, 5, 10, 15, 20 | DCS 1800, "1800" | Finland,[18] Hong Kong[19][20] |
| IV (4) | 1710 MHz to 1755 MHz | 2110 MHz to 2155 MHz | FDD | 1.4, 3, 5, 10, 15, 20 | AWS, "1.7/2.1 GHz" | US, Latin America |
| V (5) | 824 MHz to 849 MHz | 869 MHz to 894 MHz | FDD | 1.4, 3, 5, 10 | Cellular 850, UMTS850 | US, Australia |
| VI (6) | 830 MHz to 840 MHz | 875 MHz to 885 MHz | FDD | 5, 10 | UMTS800 | Japan |
| VII (7) | 2500 MHz to 2570 MHz | 2620 MHz to 2690 MHz | FDD | 5, 10, 15, 20 | IMT-E, "2.5 GHz" | EU |
| VIII (8) | 880 MHz to 915 MHz | 925 MHz to 960 MHz | FDD | 1.4, 3, 5, 10 | GSM, UMTS900, EGSM900 | EU, Latin America |
| IX (9) | 1749.9 MHz to 1784.9 MHz | 1844.9 MHz to 1879.9 MHz | FDD | 5, 10, 15, 20 | UMTS1700 | US, Japan |
| X (10) | 1710 MHz to 1770 MHz | 2110 MHz to 2170 MHz | FDD | 5, 10, 15, 20 | UMTS,IMT 2000 | Brazil, Uruguay, Ecuador, Peru |
| XI (11) | 1427.9 MHz to 1452.9 MHz | 1475.9 MHz to 1500.9 MHz | FDD | 5, 10, 15, 20 | PDC | Japan (Softbank, KDDI, DoCoMo)[21] |
| XII (12) | 698 MHz to 716 MHz | 728 MHz to 746 MHz | FDD | 1.4, 3, 5, 10 | ||
| XIII (13) | 777 MHz to 787 MHz | 746 MHz to 756 MHz | FDD | 1.4, 3, 5, 10 | Verizon's 700 MHz Block C | |
| XIV (14) | 788 MHz to 798 MHz | 758 MHz to 768 MHz | FDD | 1.4, 3, 5, 10 | 700 MHz Block D | |
| XVII (17) | 704 MHz to 716 MHz | 734 MHz to 746 MHz | FDD | 1.4, 3, 5, 10 | AT&T's 700 MHz Block B | |
| XXXIII (33) | 1900 MHz to 1920 MHz | TDD | 5, 10, 15, 20 | |||
| XXXIV (34) | 2010 MHz to 2025 MHz | TDD | 5, 10, 15 | |||
| XXXV (35) | 1850 MHz to 1910 MHz | TDD | 1.4, 3, 5, 10, 15, 20 | |||
| XXXVI (36) | 1930 MHz to 1990 MHz | TDD | 1.4, 3, 5, 10, 15, 20 | |||
| XXXVII (37) | 1910 MHz to 1930 MHz | TDD | 5, 10, 15, 20 | |||
| XXXVIII (38) | 2570 MHz to 2620 MHz | TDD | 5, 10 | EU | ||
| XXXIX (39) | 1880 MHz to 1920 MHz | TDD | 5, 10, 15, 20 | |||
| XL (40) | 2300 MHz to 2400 MHz | TDD | 10, 15, 20 | IMT-2000 | China | |
[edit]Technology Demos
- In September 2006, Siemens Networks (today Nokia Siemens Networks) showed in collaboration with Nomor Research the first live emulation of a LTE network to the media and investors. As live applications two users streaming an HD-TV video in the downlink and playing an interactive game in the uplink have been demonstrated.[22]
- The first presentation of an LTE demonstrator with HDTV streaming (>30 Mbit/s), video supervision and Mobile IP-based handover between the LTE radio demonstrator and the commercially available HSDPA radio system was shown during the ITU trade fair in Hong Kong in December 2006 by Siemens Communication Department.
- In February 2007, Ericsson demonstrated for the first time in the world LTE with bit rates up to 144 Mbit/s[23]
- In September 2007, NTT docomo demonstrated LTE data rates of 200 Mbit/s with power consumption below 100 mW during the test.[24]
- In November 2007, Infineon presented the world’s first RF transceiver named SMARTi® LTE supporting LTE functionality in a single-chip RF silicon processed in CMOS [25][26]
- At the February 2008 Mobile World Congress:
- Huawei demonstrated Long Term Evolution ("LTE") applications by means of multiplex HDTV services and mutual gaming that has transmission speeds of 100 Mbps.
- Motorola demonstrated how LTE can accelerate the delivery of personal media experience with HD video demo streaming, HD video blogging, Online gaming and VoIP over LTE running a RAN standard compliant LTE network & LTE chipset.[27]
- Ericsson demonstrated the world’s first end-to-end LTE call on handheld[7] Ericsson demonstrated LTE FDD and TDD mode on the same base station platform.
- Freescale Semiconductor demonstrated streaming HD video with peak data rates of 96 Mbit/s downlink and 86 Mbit/s uplink.[28]
- NXP Semiconductors demonstrated a multi-mode LTE modem as the basis for a software-defined radio system for use in cellphones.[29]
- picoChip and Mimoon demonstrated a base station reference design. This runs on a common hardware platform (multi-mode / software defined radio) with their WiMAX architecture.[30]
- In April 2008, Motorola demonstrated the first EV-DO to LTE hand-off - handing over a streaming video from LTE to a commercial EV-DO network and back to LTE.[31]
- In April 2008, LG Electronics and Nortel demonstrated LTE data rates of 50 Mbit/s while travelling at 110 km/h.[32]
- In April 2008 Ericsson unveiled its M700 mobile platform, the world’s first commercially available LTE-capable platform, with peak data rates of up to 100 Mbit/s in the downlink and up to 50 Mbit/s in the uplink. The first products based on M700 will be data devices such as laptop modems, Expresscards and USB modems for notebooks, as well other small-form modems suitable for consumer electronic devices. Commercial release is set for 2009, with products based on the platform expected in 2010.
- Researchers at Nokia Siemens Networks and Heinrich Hertz Institut have demonstrated LTE with 100 Mbit/s Uplink transfer speeds.[16]
- At the February 2009 Mobile World Congress:
- Huawei demonstrated the world' s first unified frequency-division duplex and time-division duplex (FDD/TDD) long-term evolution (LTE) solution.
- Aricent gave a demonstration of LTE eNodeB layer2 stacks.
- Setcom Streaming a Video [33]
- Infineon demonstrated a single-chip 65 nm CMOS RF transceiver providing 2G/3G/LTE functionality[34]
- In May 2009 Setcom Streaming HD Video at GSMA MWC and LTE World Summit
- In August 2009, Nortel and LG Electronics demonstrated the first successful handoff between CDMA and LTE networks in a standards-compliant manner [35]
訂閱：
文章 (Atom)