Brief introduction
Independent networking mode (SA)
SA refers to a new network 5G, including the new base station, backhaul and a core network. SA introduces a whole new network elements and interfaces at the same time, the network will be large-scale adoption of virtualization, software-defined networks and other new technologies, combined with 5GNR, while its protocol development, network planning and deployment of interoperable technical interoperability challenges will beyond 3G and 4G systems.
Dependent networking mode (NSA)
NSA non-independent networking refers to the use of existing infrastructure, 4G, 5G network deployment. 5G carrier NSA based architecture only carries user data, which control signaling is still transmitted through the 4G network .
It can be said, SA is pure 5G, access, throughput, latency can achieve the best performance. NSA borrowed 4G devices evolved version of 5G. In fact, 3GPP architecture for 5G standardization process, at the earliest output is 5G NSA (non-independent network), 5G can not work alone, just as a reinforcement of 4G, the 4G-sharing traffic. The standardization 5G SA (independent network) is a full six months slower than non-independent network.
Why NSA?
A: The poor, SA too burn. LTE was built, you told me to throw, play 5G? Sorry, I can not afford that!
5G network architecture
For 5G network architecture, the 3GPP TSG-RAN 72 plenary meeting of the proposed eight options, as shown below:
This option is divided into eight independent networking and non-independent networking groups. Which is independent networking options 1,2,5,6, 3,4,7,8 non-independent networking options. Non-independent networking options 3,4,7 there are different sub-options.
Option 1 has already been realized in these options in 4G structure, options 6 and 8 only theoretical existence of deployment scenarios, does not have the actual deployment of value, the standard will not be considered.
Why do so many combinations?
4G, 5G facilities construction, costly, is the largest base, in order to promote 5G commercial, 3GPP members who had gone to great pains to have all the possible impossible raised, then standardize several options feasible for operators to choose from.
Independent networking SA
Option 1
Option 1, in fact, this is pure 4G network architecture, as shown below:
Wherein the dotted line represents the control plane, the solid line represents the user plane.
However, options 1 and 5G clearly not a dime of the relationship!
Option 2
Option 2, the most simple architecture, is connected to the base station 5G 5G core network, which is the ultimate form of 5G network architecture can support all the applications 5G.
But the ultimate form usually go through several incarnations in order to achieve that China Mobile had nearly 2.3 million 4G sites, all replaced 5G? Just kill him forget.
Option 5
Option 5, note that this upgrade to enhance the 4G base station, and then connected to the core network 5G, in essence, is 4G. That original 4G core network first out of service, the base station to transform what continue to use.
However, after the transformation of the Enhanced 4G base stations compared with 5G base station, there are still significant differences in the peak rate, latency, capacity and so on. Subsequent optimization and evolution, enhanced 4G base station can not necessarily support. Therefore, Option 5 5G architecture said to be false nor wrong.
Option 6
Option 6, the 5G 4G base station is connected to the core network,
5G base station so strong so no, 5G as a base to spend the bulk are built, does not even built the core network is relatively small 5G head? Therefore, this architecture is not going to have a choice of carriers, 3GPP standardization is not considered.
SA summary
To sum up, independence 5G network program may only options 2 and 5, in which the Option 2 is the ultimate 5G network architecture.
Option 2 the following advantages:
1, is introduced in one step 5G 5G core network and a base station, it does not rely on existing 4G networks, the shortest path evolution.
2, the new 5G 5G base station and core network to support all the new features 5G network and the introduction of new services.
At the same time, Option 2 corresponding disadvantages as follows:
1,5G LTE frequency is relatively high, it is difficult to achieve continuous coverage of the initial deployment, there will be a lot of switching between systems 4G and 5G, the user experience is not good.
2, the initial deployment cost is relatively high, the base station can not effectively use the existing resources 4G.
Non-independent networking NSA
I said earlier, there are non-independent networking options 3/4/7/8, do you think this is over? Still too young, you think like this:
In fact, he is like this:
Why have these sub-options?
5G many non-independent networking options, answer three questions are arranged by the following combination:
warm up
Several terms first explained:
Dual Link : As the name suggests, is the mobile phone simultaneously with all 4G and 5G communicate simultaneously downloading data. In general, there will be a master and the connection from the connection.
We can imagine the double connection we used headsets, two-way data can be transmitted by around one pair of headphones.
控制面锚点：双连接中的负责控制面的基站就叫做控制面锚点。
不妨继续以耳机做比喻，控制面就像耳机中的控制按钮，有控制按钮那一侧一样既可以控制播放也可以发送数据。
分流控制点：用户的数据需要分到双连接的两条路径上独立传送，但是在哪里分流呢？这个分流的位置就叫分流控制点。
选项3系列
在"3系"组网方式中，参考的是LTE双连接架构，4G基站是主站，5G基站是从站：
该系列的基站连接的核心网是4G核心网，控制面锚点都在4G，UE采用双连接，同时连接4G和5G基站。5G基站无法直接连在4G核心网上面，它会通过4G基站接到4G核心网。
- 选项3：5G基站的用户面和控制面都通过4G基站连接到核心网。由于传统4G基站能力有限，这种情况需要对4G基站增强改造。
- 选项3a：5G基站的用户面直接通4G核心网，控制面继续锚定于4G基站。
- 选项3x：把用户面数据分为两部分，会对4G基站造成瓶颈的那部分，迁移到5G基站。剩下的部分，继续走4G基站。
营运商您看看，哪种喜欢挑哪种！
实际上3/3a/3x组网方式，是目前国外运营商最喜欢的方式，原因很简单：
1、利用了旧的4G基站，省钱。
2、部署起来很快很方便，有利于迅速推入市场，抢占用户。
7系组网方式
把"3系"组网方式里面的4G核心网替换成5G核心网，这就是"7系"组网方式。
需要注意的是，因为核心网是5G核心网，所以此类方式下，4G基站都需要升级成增强型4G基站。
4系组网方式
在"4系"组网里，4G基站和5G基站共用5G核心网，5G基站为主站，4G基站为从站。
唯一不同的，选项4的用户面从5G基站走，选项4a的用户面直接连5G核心网。
NSA与SA比较
1、NSA的优势在哪儿？
SA架构相比较而言更为简单，而NSA架构则略为复杂。相较SA，NSA的优势主要包括：
（1）借助目前成熟的4G网络扩大5G 覆盖范围。由于手机终端发射功率有限，所以5G网络的覆盖范围主要受限于上行（即手机发送信号到基站），那么通过与4G联合组网的方式（NSA）可以实现5G单站覆盖范围的扩大；
（2）NSA标准更早结束，产品更成熟。NSA相较SA标准更为提前，产品路标也相应的提早成熟。当前我国5G推进组也已经基本完成了NSA的大部分测试工作；
（3）无需建设新的核心网。NSA组网下，5G基站将利用现有4G核心网，省去5G核心网络的建设。
2、相较SA，NSA架构也有如下劣势
（1）仍必须改动4G现网。如上所述，NSA是4G网络和5G网络融合的组网方式，所以势必涉及到对4G现网的升级改造（包括无线和核心网）；同时5G NR应用频段更高，覆盖范围更小，现有4G网络密度无法满足5G覆盖。
（2）无法调整现有设备的供应商结构。NSA组网方式下，更加依托于原有的设备投入，采用NSA需要互操作的统一性，仍然需要采购原网厂商的设备，则运营商不能重新划分设备厂商的投资结构。
（3）现网无法满足5G高可靠低时延要求。由于NSA无需建设5G新核心网，且NSA需借助4G无线空口（NSA无线锚点在4G），但现有的4G核心网架构和4G空口却无法满足5G对于时延和传输可靠性的要求。
3、NSA架构有助于快速建网，但较SA直接建网资本开支更高
Under the premise of continuous coverage, regardless of SA or NSA dense urban scene desired 5G same number base. Taking into account the domestic 4G network now in dense urban station spacing has been within 300 meters through the analysis of 5G base station link budget dense urban outdoor scene, we believe that the basis of the 4G / 5G base station site altogether on, SA network architecture 5G continuous coverage of the scheme can be realized (NSA architecture, the need to 5G and 4G base station site altogether); single base station SA price advantage. Since the NSA needs to 5G and 4G with vendors, and SA does not have this requirement. Therefore, under the NSA architecture, operators bargaining power in sourcing 5G base station is bound to weaken.
To sum up, in general, in any event networking, and ultimately bound to SA architecture. Currently 5G commercial license has been paid in advance, in order to seize market starting 5G, NSA or networking will be the early part of the operator's choice. SA but all the tests will soon be completed.
