I have been looking for information about 1-hop neighbors on link layer in specification of the protocol.
Unfortunately I could not find the answer to my question. Has a node in 802.15.4 MAC protocol, information about its 1-hop(directly connected) neighbors?
The IEEE802.15.4 standard defines the PHY and MAC layer, thus communications and everything actually that the standard defines is for one hop communications.
The PAN coordinator is the only device that has information about other nodes in a IEEE802.15.4 context. However this only happens in what IEEE802.15.4 defines as a star topology. There are two types of topologies defined in IEEE802.15.4 Star and P2P. Star topologies are rarelly used, since a P2P topologies allow decentralized communications and it is much more flexible. P2P is the base of mesh networks. Mesh networks (multi-hop) are not covered by IEEE802.15.4.
The key section you should read to understand this is section "5.2 Network topologies", page 13 in IEEE802.15.4-2003. It clearly states: "A peer-to-peer network can be ad hoc, self-organizing and self-healing. It may also allow multiple hops to route messages from any device to any other device on the network. Such functions can be added at the network layer, but are not part of this standard."
As you can see, IEEE802.15.4 is all about one hop communications. If you are interested in multi-hop communications you should be looking at upper layer protocols that work with IEEE802.15.4 P2P topologies such as Thread or ZigBee. These protocols define how the mesh should be formed in a P2P topology.
For example: Routers in Thread networks have a Router Table, with information such as link cost as a function of RSSI using RIP. With RIP, each router knows what is the "next-hop" to reach an other router. Each router has MAC Short Address such as 0xab00 and the child's or "End-Devices" have Short Addresses of this router have MAC Short Addresses such as 0xabxx. These MAC addresses are mapped into IPv6 mesh local addresses.
I could go into more detail about routing, but what's important to understand is that IEEE802.15.4 as a PHY and MAC specification, is all about one-hop (OSI 1 and 2). If you invoke multi-hop, now you are talking about the network layer (OSI 3).
