Table 7-1 compares the IP over DCC solution, the inband DCN solution, and the HWECC solution.
Table 7-1 Comparison between the IP over DCC solution, the inband DCN solution, and the HWECC solution
DCN Solution Advantage Disadvantage
IP over DCC In the IP over DCN solution, DCN information is
transmitted over microwave DCCs without using service bandwidth.
Limited DCN bandwidth is available.
DCN information cannot be transmitted through FE/GE ports.
Inband DCN In the inband DCN solution, DCN information is
transmitted through microwave or FE/GE ports.
This solution covers more scenarios.
Sufficient DCN bandwidth (512 kbit/s by default) is available. In addition, bandwidth expansion is supported.
Part of service bandwidth is used.
VLAN resources are used.
HWECC HWECC is preferred as the
DCN solution when the network is only comprised of the OptiX RTN equipment that supports the HWECC protocol stack.
The HWECC solution is easy to configure and use.
As the HWECC protocol is a proprietary protocol, the HWECC solution is inapplicable to network management when the network is comprised of OptiX RTN equipment and third-party equipment.
7.1.2 GNE and Non-GNE
A gateway NE (GNE) refers to an NE whose application layer communicates directly with the NMS application layer. A non-GNE refers to an NE whose application layer communicates with the NMS application layer by forwarding data through the GNE application layer.
GNE
Generally, a GNE is connected to the NMS through a local area network (LAN) or wide area network (WAN). Its application layer can directly communicate with the NMS application layer.
One set of NMS needs to be connected to one or more GNEs.
ECC communication between the GNEs may create an oversized DCN. To prevent this, disable extended ECC for the GNEs.
Non-GNE
A non-GNE communicates with the GNE through the DCN channels between NEs. It is recommended that fewer than 50 non-GNEs are affiliated to a GNE.
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7.1.3 NE ID and NE IP Address
The ID and IP address are the unique NE on the DCN.
NE ID
At the application layer of each DCN solution, an NE uses its NE ID as the NE address. Therefore, each NE must have a unique NE ID on the DCN and all these NE IDs must be planned in a unified manner.
The NE ID has 24 bits. The most significant eight bits represent the subnet ID (or the extended ID) and the least significant 16 bits represent the basic ID. For example, if an NE ID is 0x090001, the subnet ID is 9 and the basic ID is 1.
NE IP Address
An NE uses an IP address as its unique identifier during TCP/IP communication.
In the DCN solutions (for example, IP over DCC and inband DCN) where network management messages are transmitted over TCP/IP, an NE IP address is used as the NE address at the network layer. Therefore, each NE IP address on the DCN must be unique and all these NE IP addresses must be planned in a unified manner.
By default (which indicates that an NE IP address is never manually changed), this NE IP address is automatically changed to 0x81000000 + ID if the NE ID is changed. For example, if an NE IP address is never manually changed, this NE IP address is automatically changed to 129.9.0.1 when the NE ID is changed to 0x090001. Once an NE IP address is manually changed, the interlocking relationship between the NE ID and NE IP address no longer takes effect.
It is recommended to configure the IP address of a GNE on a different network segment from the IP addresses of its non-GNEs.
7.1.4 Physical Boards and Logical Boards
The NE software and NMS consider a physical board as one or more logical boards when managing the physical board.
Table 7-2 provides the mappings between the physical boards and logical boards.
Table 7-2 Mappings between the physical boards and logical boards
Physical Board Logical Board
CSH CSH in the same slot
AUX AUX in the same slot
Physical Board Logical Board
FAN FAN in the same slot
ODU ODU in the slot whose number is 20 plus the
slot number for the IF board that is connected to the ODU
7.1.5 Adaptive Modulation
The adaptive modulation (AM) technology adjusts the modulation scheme automatically based on channel quality.
When the AM technology is used, in the case of the same channel spacing, the microwave service bandwidth varies according to the modulation scheme; the higher the modulation efficiency, the higher the bandwidth of the transmitted services. With the QoS technology, packet services are scheduled to queues with different priorities. The services in different queues then are
transmitted to a microwave port by using the queue scheduling algorithms. Under all channel conditions, the service capacity varies according to the modulation scheme. Figure 7-4 provides illustrates how the modulation mode is adjusted according to varying weather condition.
l When the channel quality is good (such as on days when weather conditions are favorable), the equipment adopts a high-efficiency modulation scheme to transmit more user services.
This improves transmission efficiency and spectrum utilization of the system.
l When the channel quality deteriorates (such as on days with adverse weather), the equipment adopts a low-efficiency modulation scheme to transmit only higher-priority services within the available bandwidth and to discard priority services. If lower-priority queues are congested due to insufficient capacity of the air interface, some or all services in these queues will be discarded. This improves anti-interference capability of a radio link and therefore ensures the link availability for higher-priority services.
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Figure 7-4 Adaptive modulation
Channel capability
256QAM
32QAM QPSK
256QAM
128QAM
32QAM
128QAM
64QAM
64QAM
16QAM 16QAM
Packet services
The AM technology used by the OptiX RTN 950 has the following characteristics:
l The AM technology uses the QPSK, 16QAM, 32QAM, 64QAM, 128QAM, and 256QAM modulation schemes.
l The lowest-efficiency modulation scheme (also called reference scheme or modulation scheme of guaranteed capacity) and the highest-efficiency modulation scheme (also called nominal scheme or modulation scheme of full capacity) used by the AM can be configured.
l In AM, when modulation schemes are switched, the transmit frequency, receive frequency, and channel spacing remain unchanged.
l In AM, modulation schemes are switched step-by-step.
l In AM, modulation scheme switching is hitless. When the modulation scheme is downshifted, high-priority services will not be affected when low-priority services are discarded. The switching is successful even when 100 dB/s channel fast fading occurs.
7.1.6 CCDP and XPIC
l In single-polarized transmission, a signal is transmitted over the horizontally polarized wave or the vertically polarized wave on the same channel, as shown in Figure 7-5.
l In CCDP transmission, two signals are transmitted over the horizontally polarized wave and the vertically polarized wave on the same channel, as shown in Figure 7-6.
The capacity in CCDP transmission mode is double the capacity in single-polarized transmission mode.
Figure 7-5 Single-polarized transmission
Figure 7-6 CCDP transmission
The ideal situation of CCDP transmission is that no interference exists between the two orthogonal signals that operate at the same frequency, and then the receiver can easily recover the two signals. In actual engineering conditions, however, regardless of the orthogonality of the two signals, certain interference between the signals exists, due to cross-polarization discrimination (XPD) of the antenna and channel deterioration. To cancel the interference, the XPIC technology is adopted to receive and process the signals in the horizontal and vertical directions, so that the original signals are recovered.
The characteristics of the XPIC function supported by the OptiX RTN 950 are as follows:
l The XPD tolerance is increased, and the notch performance is improved.
l The maximum difference between the IF cables in two polarization directions of an XPIC workgroup cannot exceed 12 meters in length.
l The XPIC function is implemented totally based on hardware.
7.1.7 RF Configuration Modes
The OptiX RTN 950 supports four RF configuration modes, namely, 1+0 non-protection configuration, N+0 non-protection configuration, 1+1 protection configuration and cross-polarization interference cancellation (XPIC) configuration.
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